So I finally got to the range with my SWAT buddy. It was a good day of shooting. After a bunch of shooting, and realizing how bad I suck compared to him, we were chatting and I asked him what he thought was the "best weapon for for close range,fast encounters with life or death riding on the results." He said without hesitation he believed it was the MP5 and that it was his first choice if he is going into CQB situation. His second choice (and I must correct what I said above about him having an AR) was the G36 that he carries.
I asked him how he felt about a shotgun. He said the only thing he used it for on a SWAT call is to open doors or shoot dogs. He did recount a few tales of people getting hit with shotguns and noted that the effect on target was rather impressive (2 with slugs one with 00 buck). I asked if he wanted to use a shotgun on SWAT calls if he could and I understood his answer to be sure, he has one in his car, but he would rather have the MP5 or the G36 or an AR.
His reasons for the MP5 IIRC were at least in part the following
quickest to get on target and to move from one target to the next in general fast handling. Highly controllable in full auto (which anyone who has shot an MP5 can attest to; it is rather easy to keep a burst in a very small group), ammo capacity and reloads, and that the MP5 is extremely reliable weapon. MP5 is easily suppressed.
I didn't take anything he said to be a disparagement of the shotgun. Only that it was not his first choice. And for the civilian $250 for a pump gun is sure a lot easier to swing than 18K for a MP5
Anyways just one guys opinion, but an educated and experienced opinion.