I'm wondering if you see the same results that I do. I've noticed that if both my Xbox's are online playing in a party (same lobby, same team), that one of my Xbox's will always be laggy, while the other is in God-mode. The Xbox that's laggy changes, but about 90% of the time, it's the newer Xbox Slim. Both are hard-wired, both have equal priority in the GameFuel. Doesn't matter what game it is either, at least from the games we play together (mostly FPS's), such as COD, Battlefield, Halo, etc.
Since I know it will be asked, yes, I've followed the sticky & my firmware is 1.23NA.