Recently, I got an opportunity to configure Search in SharePoint 2013. Then I thought let me compare the difference between SharePoint 2010 and SharePoint 2013 search and then go for the SharePoint 2013 configuration.
 
Below are the some of the differences found during the analysis.
| 
Sl.No. | 
SharePoint 2010 | 
SharePoint 2013 | 
| 
1 | 
Majority of the search runs under MSSearch.exe process | 
Only crawl component run under MSSearch.exe process. Rest of the
  search components run under SharePoint Search Host Controller Service i.e.
  hostcontrollerservice.exe | 
| 
2 | 
During crawl, as items are indexed (built-in Memory), they are
  streamed/propagated to a Query server and index there. | 
During crawl, crawled items are sent over to the Content Processing
  Component for further processing. | 
| 
3 | 
Crawl freshness is poor compared to 2013 search. E.g. In SharePoint
  2010 it is easy to get into state where a very long incremental crawl would
  overlap into the next scheduled incremental crawl. This usually occurs
  because lots of security changes are being processed.  | 
SharePoint 2013 improves the crawl freshness tremendously using
  Continuous and Cleanup crawl. | 
| 
4 | 
In SharePoint 2010 search, crawl component is ultimately responsible
  for extracting metadata, links and property mappings. | 
In SharePoint 2013 search, the Content Processing Component performs
  the document parsing, metadata extraction, links and property mapping. | 
| 
5 | 
In SharePoint 2010, the web analytics service application is
  responsible for analytics processing. | 
All analytics processing is performed by the Analytics Processing
  Component within Search Service Application. | 
| 
6 | 
Whenever document is changed/updated, the entire document will be
  re-indexed and propagated to query server. | 
The index is more efficient in SharePoint 2013 search. Because it’s
  been broken into update groups. A single crawled document could be indexed
  across several different update groups. Each update groups contains a unique
  portion of the index. This allows for partial updates which means if I make a
  changes to a document, only that change is updated within the index of the
  associated update group instead of entire document. | 
| 
7 | 
Query runs under MSSearch.exe and retrieves properties from the
  Property Store database and invokes Search Administration database for
  security trimming. | 
Query Processing Component now under noderunner.exe and no longer
  retrieves properties from the property store or invokes the Search Admin
  database for Security Trimming when processing a query. It only fetches
  results from index components which simplifies things tremendously. | 
| 
8 | 
In SharePoint 2010 Search, each crawl component is mapped to crawl
  database which is 1:1 relationship.  | 
The relationship between crawl component and crawl database is doesn’t
  exist in SharePoint 2013 Search. So a crawl component will automatically
  communicate with all crawl database if there is more than one. | 
| 
9 | 
To gain fault tolerance in SharePoint 2010 Search, two crawl
  components (one mirrored) would need to be provisioned per crawl database. | 
Since there is no unique relationship between crawl component and
  crawl database, SharePoint 2013 Search automatically gains fault tolerance by
  simply provisioning a new crawl component. | 
| 
10 | 
Installation: Different
  installation for SharePoint 2010 and FAST Search. | 
Installation: Single
  installation in SharePoint 2013. | 
| 
11 | 
Crawling Components:
  Multiple crawl components on single server but each component was associated
  with only one crawl database. | 
Crawling Components:
  No unique relationship maintained between crawl components and crawl
  database. All crawl component can talk to all crawl database. | 
| 
12 | 
Host Distribution: In
  SP2010, you could pick certain crawl components to crawl a particular URL. | 
Host Distribution: Host
  can be distributed across multiple crawl databases. The new distribution happens
  on the basis of Content DB ID rather than host URL. | 
| 
13 | 
Content Processing
  Customization: In SP 2010, we had pipeline extensibility. Which let
  you write custom code to use in the transformation of crawled content before
  it got added to the index. | 
Content Processing
  Customization: In SP 2013, the pipeline extensibility model has gone.
  But it has been replaced with new web service called out feature. It is
  invoked via triggers which you create and are based on the value of the
  different managed properties. | 
| 
14 | 
Security Information:
  Search Admin DB is storing the security information (ACL Information). | 
Security Information:
  Search Admin DB is NOT storing any security information (ACL Information). It
  is storing with index itself. | 
| 
15 | 
Built in BDC Connector:
  No Documentum Connector OR Term Store Connector. | 
Built in BDC Connector:
  New built-in Document Connector and Term Store Connector are available in SP
  2013. | 
| 
16 | 
HTTP Site Crawling:
  Anonymous crawling was not supported into SP 2010 for HTTP Site. | 
HTTP Site Crawling:
  Anonymous crawling is available in SP 2013 for http sites. | 
| 
17 | 
Crawling - Continuous Crawl:
  This feature doesn’t exist in SP 2010 Search. | 
Crawling - Continuous Crawl:
  Continuous crawl feature is available in SP 2013 Search only for SharePoint sources. The default interval for this is 15
  minute and can be changed through PowerShell commands. | 
| 
18 | 
Indexing - Remote SharePoint
  Source: This functionality is not available in SharePoint 2010
  Search. | 
Indexing - Remote SharePoint
  Source: A new feature to index “Remote
  SharePoint Sources” is available in SP 2013 Search in which we can crawl
  a remote SharePoint Farm in different Geo locations using “oAuth Trust” which removes the issues
  of “Kerberos” authentication
  between the farms. | 
| 
19 | 
Search Sources: In
  SP 2010 Search, scopes can only be created by Search Service Admin. | 
Search Sources: In
  SP 2013 Search, Site and Site Collection Admin can configure the result
  sources for a site collection. | 
| 
20 | 
Data Source:
  Exchange is not a data source | 
Data Source:
  Exchange is a data source for a Result Source. | 
| 
21 | 
Query Transformation for a
  Result Source: Not Applicable | 
Query Transformation for a
  Result Source: Query transformation can be applied for a Result
  Source. | 
| 
22 | 
Indexing PDF Support:
  Advanced filter pack/iFilter being used in SP 2010. | 
Indexing PDF Support:
  Indexing PDF support is OOB feature of SP 2013 Search. | 
| 
23 | 
Format Handlers:
  Not Applicable | 
Format Handlers: New
  parsing feature in SP 2013 Search. 
Automatic File Format Detection: No longer relies on file
  extension. Deep link extraction for Word and PowerPoint formats. 
Visual Metadata Extraction: titles, authors and dates 
High performance format handlers for HTML, DOCX, PPTX, TXT, Image,
  XML and PDF Formats. | 
| 
24 | 
New Filters for Visio and
  OneNote: Not Applicable | 
New Filters for Visio and
  OneNote: Available in SP 2013 Search. | 
| 
25 | 
Schema Management:
  Search Service Application Admin can only create “Crawled” & “Managed”
  properties available to the entire farm. | 
Schema Management: Capability
  to do the limited schema management down to Site Collection Admins. Site
  Collection Admin can create custom crawled and managed properties that are
  only used in their site collection. The managed properties that can be
  created are limited – that means they cannot be refinable or sortable and it
  only supports text data type. | 
| 
26 | 
Schema Management:
  In SharePoint 2010 Search, you had to do one FULL crawl of all your contents
  to create a crawled property. You could then create a managed property and
  map it to the crawled property. But you had to do a second FULL of all your
  contents to populate it with data. | 
Schema Management: That
  is no longer required in SharePoint 2013 Search. To begin with when you
  create Site Column, it automatically create crawled properties out of it
  right then and there – no other FULL crawl required. Secondly after you
  create managed property and map it to your crawled property, you NO longer
  need to crawl the entire farm. Instead you can go into the list or library
  and there is an option now to Re-Index the list. Alternatively, you can go to
  the site level and choose to Re-Index the Site. | 
| 
28 | 
Query Spelling Corrections:
  Default spelling dictionaries and Query Spelling Inclusions list. | 
Query Spelling Corrections:
  Customization to Query Spelling Correction is now managed in term store –
  both inclusions and exclusions. In addition to that we still have a dynamic
  dictionary that is based on content in the index itself, or you can also still
  choose to go with a static dictionary. | 
| 
29 | 
Query Rules:
  SharePoint 2010 query is simple i.e. one query has one set of results. | 
Query Rules: Query
  rules allow you to have search requests from a user trigger multiple queries
  and multiple results sets. | 
| 
30 | 
Display Templates:
  Not Applicable | 
Display Templates: A
  display template is applied to the result based on the result type that it
  matches. You can define your own Custom Display Type. | 
| 
31 | 
Thumbnail Preview:
  Thumbnail preview was available for Office documents with preview of first
  page in word and 3 slides in PPT. | 
Thumbnail Preview: With
  new web app engine, you can browse through entire document in the preview. 
-         
  See all pages, animations, zoom in/out, and
  scroll through the entire document. 
-         
  The point of this is to allow users to find the exact item they are looking for right in
  search results – no more clicking a result, hitting back button and on
  and on until they find the one they are looking for. 
Previews only work with claims authentication and doesn’t work with
  Classic Windows Authentication. | 
| 
32 | 
Search Portability:
  Not Applicable | 
Search Portability:
  Search portability supports transferring the following items 
-         
  Result Sources 
-         
  Query Rules 
-         
  Result Types 
-         
  Schema 
-         
  Custom Ranking Models 
Transferring can happen between a tenant, site collection or site
  using export/import search configuration option of CSOM (Client Side Object
  Model). | 
Hope this helps and I would request to update me if you find some more in terms of technical / functional.
Have a nice day!!!!
 


