Can't find a definitve answer on TechNet:

Exchange 2013 SP1 deployment

What's the implications for deployment on Server 2012 vs Server 2012 R2?

(License issue stopping use of Server 2012 R2)

Any loss of functionality by going non-R2?

Thx

Here is what you will be missing in terms of Exchange

http://blogs.technet.com/b/scottschnoll/archive/2014/02/25/database-availability-groups-and-windows-server-2012-r2.aspx

While your users won't notice a difference in functionality its always best to be on the most recent server version as possible. But if you can't do it you will be OK with 2012.

2012 R2 includes Powershell v 4.0, 2012 comes with Powershell v 3.0. If you have scripts ritten in 2012 R2 they may not run correctly on 2012 (I hit that issue myself)

• Proposed as answer by David Wang_Microsoft contingent staff 4 hours 54 minutes ago

On the reverse, Given the choice, I cant think of any reason to use regular 2012 over R2.  Note that a lot of the cluster hotfixes required in the original 2012 are built-in to R2, so that's a bonus.

Anecdotally, I have seen fewer VSS backup issues with Exchange and R2 than with Exchange and original flavored 2012.