People stop saying the G2 and Galaxy S line up are almost identical. First off, we don't really know until we see dogfights, but even then the hardware just isn't as good. Adreno205 is an Xbox 360 while the PowerVR chip is a PS3. For basic needs they will perform identical almost, but for more heavy processes the PowerVR is the better chip by a long shot.
I would say go with the Epic 4G, the keyboard on that thing is amazing. I used one at the Sprint store and was pretty surprised at how nice it was. Samsung is really doing their thing right now, I'm tired of these 4 row keyboards.