The biggest debate on the pump 12ga is the Remington 870 vs mossberg 500. Both have an endless supply of accessories. They are both extremely reliable. You can not go wrong with eater of these. Both used by military and law enforcement.
I have a 870 in 3 1/2" after thousands of rounds I have never had a problem. A buddy of mine has a 870 3" he keeps in his toolbox. We usually shoot skeet every other Sunday. He has never cleaned it not even once since he bought it about 5 years and 4,000 to 5,000 rounds ago. It has never had a ftf or any other problem. He dose have minor surface rust due to leaving in in his truck toolbox and never cleaning it.