I have 3 pump guns, a 1976 870 Wingmaster with a 12.5" barrel, a Mossberg 590 20", and a Mossberg 500 18.5". The 870 is the prettiest and has the smoothest action but the Mossbergs have a better safety, lighter aluminum receiver, and are faster and easier to reload with out the lifter in the way like the 870. My 500 is smooth and the lightest of the 3 but on a tactical shotgun I really want to have mag tube the same length of the barrel. As of now my go to defensive shotgun is my 590 as it is set up with a side saddle, tritium bead, L3 intigrated fore end light, and Hogue 12" LOP stock.
To the original question it you are set on an 870 I would highly recommend an older Wingmaster over a newer 870, I got mine in excellent condition for $275 off the EE and sold the 28" barrel for $150. It is much nicer then my friends 870 Express.