The CPU, which is by far the most important value in determining SIM speed, is not as fast as you seem to think. Assuming stock clock, an e8400 3.0ghz, which is not even remotely cutting edge si already something like 40% faster (passmark). There might also be some favorization towards intel when it comes to the programming as well since Intel CPU have a much larger market share. All in all, I'm not that surprised seeing those numbers in a 3v3 or especially a 4v4. Singleplayer runs much smoother for me than multi as well, though 2-8 seems like a large gap.