For development, nope, no advantage, unless you're doing GPU development. A Mac Pro is slightly faster at 4 cores, but the price really isn't worth it.
Compiling code is all CPU, and some disk, so other components simply don't factor in at all. Get a well configured iMac or Mac Mini with an SSD and quad core if you're looking at a 4 core Mac Pro for coding, and you'll save a lot of money while getting similar performance. Or heck, get a Retina Macbook Pro, which is less money, but will probably beat a MP in CPU performance due to being a Haswell part.
If you're looking at a 6-12 core Mac Pro, that's different.
I really doubt any people saying I don't know what I'm talking about have spent much time, or any time, doing development. There is nothing a 4 core Mac Pro will get you for development over a lot of other machines.
Yes, the iMac doesn't have a changeable display, but for the cost of the Mac Pro, I could buy two iMacs. I could either keep a spare under my desk, or buy another one in two-three years when they get upgraded. Again, at a higher performance than a 4 core Mac Pro.