The issues with pumps is that they are a compromise gun - while they can be used for a lot of activities, they are not the best choice for too many, if any, at all.
Clay games that require a second shot especially show the disadvantage that a pump offers - O/U wins that hands down, semi in distant 2nd.
Waterfowl with the uber-loads? Semi wins hands down
CAN a pump be used? Sure, and for a very few folks, it works well - however, it seems the folks always recommending the 500 or 870 have never owned or shot a serious semi or O/U in competition, where one missed bird can relegate you from first to worst
So it will come down to what the OP's desire is - personally, as has been mentioned, get a good semi for targets and a used pump for HD