They may pattern well...but every one that I have touched, including the one I owned, felt like a piece of junk. Yes, this is a very subjective thing, but a very real issue for me. Perhaps this is because I have used 870s for so long, perhaps its some other unknown bias, but I simply cannot abide by the loose and cheap feel of the guns.
As for 870s...yes, the newer ones are somewhat lacking, but even the shoddiest Express is something I would pick over any Mossberg. That being said, with so many on the used market, its not really an issue. You can pick up an older Express with choke tubes for $200 bucks without even looking hard, and less if you are willing to shop. Older Wingmasters and Police guns are out there as well, and for not much more money.
The Nova...I might pick one over a Mossberg, but it would be a tight race.