The Evo's camera is not very good in low light compared to a Galaxy S phone (assuming the Epic has the same camera sensor as the Galaxy S i9000). Megapixels mean absolutely nothing on the Evo, nor on any phone I have had. It claims that it can get expanded to 8 Megapixels (someone help me out with the exact resolution here, thanks!), but I start seeing some pretty bad problems after putting it at 1440x900. The photos just look really terrible IMO, but of course, I have not tried customizing the settings too much. The i9000 looks really good at 1440x900 in low light.
As for me, I returned my Evo and will be getting an Epic 4g. I really think that Samsung will be different about updates on this phone (I have owned an Instinct and there actually were quite a few software updates, although I still hated the phone). I loved Sense, but I'm over it now because I actually kind of like Touchwiz 3.0. All in all, it comes down to personal preference, but for me, I just see a few more important things for me in the Epic than in the Evo.