Depends really on what you do with it.
If you play with v-sync enabled, in most games you won't feel a difference, in my opinion.
Some newer games may be a little choppier with 1280x1024 resolutions.
You will feel the lower memory speed when doing anti-aliasing, I think, because of the larger textures. Especially since DDR doubles the deficiency of the memory clocking of the OEM version.
And I read that although the core is easy to overclock, the RAM is not as easy, depending on the manufacturer.
If you do not need dualhead capabilities, the GeForce 3 may be the better deal for you. If you want dualhead though, either one is a sweet deal, the retail will last you a little longer.
Edit: Last sentence: I meant either OEM or retail Radeon 8500 is a sweet deal when you want dualhead