Exchange 2010 or Exchange 2013?

Hi

We are currently running on Exchange 2007 SP3 and wish to upgrade. We have option to upgrade either to Exchange 2010 or Exchange 2013. As there are a number of changes made to Exchange 2013 (no MAPI support, only two roles and lesser number of supported databases in Enterprise version etc), need to know what are the areas to look for when planning to upgrade from Exchange 2007. Specifically things like:

1. Applications that relay e-mail using Exchange (MAPI)
2. Exchange Server 2007 SP3 + update rollup 10. This requires preparation of the existing Exchange 2007 infrastructure
3. Outlook 2013 is supported as-is by Exchange 2013, but an update is required for Outlook 2010 and 2007. This requires preparation of the client infrastructure

Request people in the community to contribute their views on this.

Thanks

Taranjeet Singh

zamn