Alot depends on WHICH pump and which Semi-auto we are talking about.
I have quite a few sporting shotguns...none are short barrel models...never saw a point in the combat shotguns once I was out of the military. I've always figured if I have to use it for HD, a BG won't care if the shotgun he gets shot with doesn't have a pistol grip or a short barrel
I own an 11-87, Benelli M2 and an old M1, Model 101 O/U, Browning Gold Hunter, and an old Winchester Mod. 12 (16 gauge)
was my grandpappy's (probably only a few years after dropping the exposed hammer). (Notice the Duck gun theme!)
The old Model 12 you just hold down the trigger and operated the slide while holding down the trigger (I think they were called riot triggers?), not sure how many are like that anymore. Each time you brought the slide forward it fired and kicked the slide back basically. Can usually keep the pellets on a "person size target at 25 yds.
The few times a year we shoot the 16ga, we can run 5 shells through it faster than the 11-87 or Browning Gold can cycle 5 shells. We can not beat the Benelli's though.