Well for one, your storage won’t be as fast as the Retina because it uses a proprietary PCI-e SSD. It’ll boot up insanely fast, but unless your workload requires it, you won’t notice it. And if you don’t even understand what I’m talking about, chances are you won’t need it.
The non-retina is 1400×900, so unless you want that IPS screen (as gorgeous as it is) and the high resolution, you’d do better going with the non-retina and installing the RAM (supports up to 16GB of DDR3, idk about the speed though so Google it) and whatever storage you want on your own.
Oh, and get the i7 😛 Even though it’s a dual-core.