I have had an 870 express for 20 years, and have had it in just about every hunting condition you can throw at it. It's always been a good solid gun and hasn't given me any real trouble. Only thing that puzzles me a little is for what has only been the last couple years, when you fire a shot and cycle the action, and pull the trigger again, all you get is a click... Sometimes it fails to release another shell from the magazine tube. I have checked everything over a hundred times... Nothing is worn, the slide bar pushes on the shell stop right when it should, and everything is nice and tight... Can't figure it out. It only seems to happen when I am excited and shooting at geese lol.
A few weeks ago, I bought a mossberg 535, and although it's nothing fancy, I have to say I love the gun. Works great, easy to take apart for cleaning, and is a better fit for me than the 870... I shoot much better with it.
The only gripes I have with the mossberg is the plug somehow got out through the side of the magazine spring and jammed the spring in the compresses position, and the magazine tube was the most aggravating thing I have ever seen to remove...mossberg doesn't spare any mercy with the thread locker. Anyway, after I finally got it apart and got the plug out of the spring, I cut a pencil to the right length, and it's been perfect since.
Best of luck with whichever gun you decide on, and happy hunting.