Mossberg 500 OR Winchester 1300
I own both.
A 500 Mossberg; A 1300 Defender; A 1300 long barrel hunting model.
In my oponion the 1300 is a smoother, faster cycling, more refined SG.
The overall quality of the Winchester is superior to that of the 500.
The 1300 is lighter as well due in part to the alloy receiver which I am 100% sold on! Some may say that the alloy receiver is weaker, thus a fault with the 1300. I disagree strongly for the following reason, which is another attribute about the 1300 that's won me over. The 1300 uses a four lug rotary lock bolt, similar to the AR-15's. It locks solidly into the chamber of the barrel and keeps pressure trapped in the barrel through the peak of the firing cycle. Because of this the receiver does NOT have to withstand the pressure. So the lighter material works! After the pressure peaks and returns to a safe level, the bolt unlocks and the remaining pressure assists the bolt traveling backwards. This makes the 1300 fast to cycle rounds. In fact it's billed as the fastest, smoothest pump action shotgun, period. And based upon my experiences I agree. The follow-up shots are so quick it almost feels like the darn thing will cycle-pump rounds on its own!.
It has dual action bars for real smooth chambering of shells and this helps prevent the action from binding-up. I've never had a binding problem with either of the 1300 that I own, in fact never a problem period.
I guess they got the name "1300 Speed Pump" for a reason, it's fast man, real fast!
I even read about it having been tested with one of those electronic timers. According to those tests the average was .56 of a second for three shots. That’s right, about a half second! Of course I'm NOT able to shoot as fast as those guys that conducted these tests. And accuracy goes out the window when cycling rounds that quickly. But I cite if to illustrate a point.
So anyway I look at it the 1300 pumps very fast and is quite strong thanks to that 4-lug rotary bolt designed system.
Like I said I actually feel it with my forward pump hand. That thing is fast! And slick!
I do however like the location of the safety on the Mossberg better than any SG I've ever owned, used or held.
BUT with that being said you'll probably be happy with either, but for me it's the 1300.