You'll find a ton of different answers for this one... I'm no expert, but I have trolled these forums quite a bit.
I believe it has more to do with the Kernel you're using. Also, it seems that ROM's, Kernels, etc., affect phones differently. The current setup I have on my Inc, may work completely different on yours.
You just have to try different combinations until you find one you're happy with.
I'm currently on CM7 RC3 with the stock Kernel. I'm very happy with it. By the time I get home in the evening, I'm at about 70% on battery. My heaviest usage is in the evening, so I charge on my way home.