which one of these PCs would you guys pick for pc gaming and why?

Solution
Since all builds share the same GPU and storage specs, only the RAM amount and CPU performance is different between the three. At today's gaming world, 16GB or RAM is more than enough. 48GB of RAM is handy if the PC would be used as a workstation build (e.g video rendering). With RAM amount out of the way, it comes down to the CPU performance.

For gaming, 1st build and it's Xeon E3-1240v3 (4 cores, 8 threads) is the best performing CPU out of all the three listed Xeon builds. Performance wise, 3rd build with Xeon X5660 (6 cores, 12 threads) comes at a second place.
E3-1240v3 vs X5660, comparison: http://cpu.userbenchmark.com/Compare/Intel-Xeon-E3-1240-v3-vs-Intel-Xeon-X5660/m4602vsm17750

Sure, the 2nd build with Xeon E5640 (4 cores, 8...

Aeacus

Titan
Ambassador
Since all builds share the same GPU and storage specs, only the RAM amount and CPU performance is different between the three. At today's gaming world, 16GB or RAM is more than enough. 48GB of RAM is handy if the PC would be used as a workstation build (e.g video rendering). With RAM amount out of the way, it comes down to the CPU performance.

For gaming, 1st build and it's Xeon E3-1240v3 (4 cores, 8 threads) is the best performing CPU out of all the three listed Xeon builds. Performance wise, 3rd build with Xeon X5660 (6 cores, 12 threads) comes at a second place.
E3-1240v3 vs X5660, comparison: http://cpu.userbenchmark.com/Compare/Intel-Xeon-E3-1240-v3-vs-Intel-Xeon-X5660/m4602vsm17750

Sure, the 2nd build with Xeon E5640 (4 cores, 8 threads) has the most amount of RAM, 48GB compared to the 16GB of the other two builds but CPU performance wise, it's the worst performing of the three,
E5640 vs X5660, comparison: http://cpu.userbenchmark.com/Compare/Intel-Xeon-E5640-vs-Intel-Xeon-X5660/m11771vsm17750
 
Solution