Provided that eVGA's 5900 Non-Ultras are still using 2.2ns memory (last time I heard they were) get the 5900. If you're an overclocker, you'll really enjoy the 5900 Non-Ultras as well, because they are EASILY clocked to 5900 Ultra speeds, and provided your system is well-cooled, 5950 Ultra speeds are definitely attainable (got my XFX 5900 NU at 5950 Ultra speeds right now) 🙂
Peace