I have a Mossy500 and a 870, both in 20Gauge for my kids. I bought the 870 first and a few of my smaller kids didn't care for it, so I purchased the 500 with the intent on selling the 870. Then... it became apparent that half my kids preferred the 500 over the 870 and vise versa... so I'm keeping them both. The 500 has more kick, but is shorter so the smaller kids can maneuver it easier, the 870 is much longer and therefore has less kick, but my oldest daughter (15) really likes it better.
So.... moral of the story ... it depends on the shooter. Both guns have worked w/o flaw and I'm happy to have both in the inventory.
Hope this helps...
Cheers