Audits and Cloud Tax
For us dropping Oracle it came basically down to two things: Audits with Oracle people who don't know their products and licensing so they try and unfairly screw you over (partner - yeah right). Cloud Tax - only allowing 1 "core" per license for x64 on anything but their own cloud (so yeah, it IS faster by default).
Can you say - hello PostgreSQL and SQL Server? PostgreSQL for the heavy lifting and spatial databases, and SS for the sleepy databases where the app can use whatever platform.