Which 15" Macbook for me?

Why $500? Upgrading from 8 to 16 GB of RAM is only $200.

 

16...

Working with relatively complex sets of data in apps like AutoCAD can consume a good bit of memory. Mavericks does a really good job of handling memory, with things like memory compression, and with the fast PCIe SSDs, swap time isn't terrible (although you definitely still want to avoid it.). My suggestion is to go for the 16gigs. You'll probably be fine with the base model's CPU and GPU, but you don't want to compromise on the memory. You can't upgrade it later, and I often push the 8 gigs in my machine, even when not doing too terribly taxing work. The money you throw at the extra memory is saved in the other end, considering that your need for buying a new computer after this one will be pushed maybe 2-3 years. If I were you, I'd definitely not compromise on the memory.

 

Enough is never enough. Or, as MTV once put it, "Too much is never enough."