I have used both the Rem 870 Super Mag (my personal waterfowling, dove, etc gun) and the Benelli Nova (a gun I bought for my father). I can wholeheartly attest to both being great, tough, dependable guns. While I initially had problems with my 870 with a burr inside the chamber that would not let me eject shells, Remington sent me a new barrel and everything works great now. I have been shooting this gun for about 4-5 years now.

Negatives with the 870:
Wood scratches WAY TOO EASILY. Only a cosmetic problem, does not hurt shooting performance.
Barrel and other metal components rust too easily. Keep it well lubed. The bluing also wears too quickly.
Looks a bit cheap.

Positives with 870 (since new barrel):
Shoots great everytime. Never a misfire or problem with the action.

The Nova I have shot only a few times. But here are the positives and negatives I have seen with it so far.

Negatives:
A very long gun. The receiver is much longer than the one on the 870 so fit may be a problem for you. Practice moving both guns up to your shoulder quickly and see what fits better for you. I would very much recommend a 26" barrel if you get the Nova since the gun with a 28" barrel and the long receiver makes for a very long gun indeed. We had a little bit of trouble finding a soft case that his gun would fit in.

A little on the heavy side but not a big diff between the Nova and the 870. Not really a big deal.

The grip on the pump action wobbles just a little too much for my taste.

Positives of the Nova:

Has a very imposing look to it.

Benelli name

Very durable

Very resistant to rust...I love the finish on this gun.

Can eject the shell in the chamber and still keep those in the magazine in place. Great for crossing fences, etc.

Sling mounts.

Easy to take down.

If I had to choose between these two, I would more than likely buy the Nova. You really can't go wrong with either one though. I just like the more durable finish and extras you get with the Benelli. Both guns do fit and feel different so definitely go with which one fits you best. BTW, both guns will shoot 2 3/4", 3", and 3 1/2" with no problem. Good luck and let me know if you have any other questions.