I have both and some of the above is true for both.
I loved my Epic, best phone I ever had until I got the Nexus for size, I don't use keyboard and didn't need the bulk.
Setting side by side (hubby kept Epic for keyboard), I get more bars in 3g area. I also found no battery issues after I rooted and put on custom rom - both phones can go 1.5 days without charging, both are
running Gingerbread roms, both are fast, mine is just faster.
So Epic stock will have battery issues, you have to read and learn some management (using Menu to close running programs such as DRM and other popups from Sprint/Samsung in menu). If you want keyboard and
want to root, this is a great choice.
If you do not need keyboard, get the Nexus - everything is already setup for you. And ignore the negatives, everyone writes to complain, or possibly enlighten, but each phone and area is different.