As a side note which ever one you purchase remember to keep it protected with some kind of rust inhibitor. This is true for any none SS gun. I have read a lot of complaints on the Internet of people having rust on their 870 Express. I'm not sure if they are more prone to rust compared to a Mossberg 500 or not. I just bought an 870 Express a few months ago and one of the first things I did is give it a good coat of Break Free CLP inside and out to prevent rust. I wasn't going to take any chances with it. I also have a Mossberg 500 and it also gets the CLP treatment. During your decision keep in mind that there is a large market of accessories for the 870 and the Mossberg 500 if you want to modify your gun any. This is not so much true with other brands.
Shooters. We are a community. United we stand divided we fall.