Difference Between 2012 and 2014 SQL Server Enterprise Edition
1. Memory Support: The earlier versions of Sql Server (i.e. 2008 R2 and 2012 only support 64 GB. On 2014 the memory support is increased to 128 GB of memory.
2. Indexes: In 2012 columnstore indexes was introduced which was a great help to datawarehouse workloads. But they were limited to non clustered indexes, supported very few number of datatypes. But in 2014 this feature was expanded to support clustered columnstore indexes and many of the datatypes restrictions was removed.
3. Buffer Pool Extension: Use of fast SSD drives that can really prove as a perfect substitutes for memory. This proves to be very grateful when the server does not support more addition to RAM memory and database size exceeding the amount of RAM.
4. The New Cardinality Estimator: The introduction to this estimator which is great at fixing a lot of queries and providing better plans without re-writing the queries themselves.
5. Always on Availability Groups: SQL Server 2014's AlwaysOn Availability Groups has been enhanced with support for additional secondary replicas and Windows Azure integration.
Reference : Raghav Mehra(C# Corner)