Well just a quick glance at passmark to make sure I am correct a Phenom II x4 980 @ 3.7ghz scored 4540, whereas the stock clocked (2.67) i7 920 scored 4947, so we have a quad core with hyperthreading form Intel at 2.67 outscoring AMD's fastest stock clock Phenom II, now as slh28 said the D0 steeping is the best, but both steppings can get the chip over 3ghz, were looking at well into the 5,000 mark now for a score, where as overclocking the phenom II is nice because of the unlocked multi, but that particular architecture usually stalls around 4ghz for a daily overclock so your not gonna see much more out of that chip. If the motherboards are the same price, since X58 used to be substantially more expensive the am3, then I would suggest the Intel, honestly gaming wise though both chips are gonna be great and should be able to handle any game. check out this techspot review, the phenom is a bit lower clocked, but just add around 3-5 FPS in most cases for gaming.
https://www.techspot.com/review/195-mainstream-quadcore-cpu-performance/page7.html , but do remember that a stock clocked i7 920 the nehalem architecture loves clock speed, and really shines at higher speeds.