As most everyone aroun dher knows I swear my the Benelli (M1). When it gets really dirty it hiccups with super light ammo (skeet loads), but I have never had trouble with full loads. Great with slugs too!
In my heart, I am sure that modern pumps are more reliable in long term tactical situations. But I think that the tactical world's aversion to semis (which is starting to fade) is a product of older semis which may not have been as reliable as the moderne ones.
The Beretta tactical semi is more sensitive to light loads, in fact, although Nashville metro officers can carry their own sem i shotguns in their PCs, they have to use issue ammo, and the issue buckshot is too light to cycle the Beretta.
With a PG stock (not just a PG..) you also get the advantage of one handed use. I have shot quite a few clays one handed with the Benelli, it is really easier than one would think, though your strong hand gets tired pretty quick.
Some day I will upgrade to a Benelli M3 and have the best of both worlds (semi/pump in emergencies).