Dave2D had xcode benchmarks and it seems like... It's faster than the iMac Pro, and even faster than his friends hackintosh. Might be the fastest, or almost the fastest, out of Apples entire lineup.
I'm looking this repo[1] for reference, something must be off, because a mid 2015 has half the time in incremental build, of course the project matters, but Dave doesn't reveal the name of the app they are compiling or I missed it.
https://youtu.be/XQ6vX6nmboU at minute 3