I don't know that .45s would have made much of a difference. Platt and Matix were "goal-oriented bad guys" or "goal-determined persons" (I have heard both descriptions for the same phenomena). Essentially, nothing short of a nervous system shutdown (brain shot or brain stem shot) was going to stop these guys. As McNeil (I Believe) said at the end of the show, "These guys were dying, but not fast enough."
My understanding from various individuals is that after taking a couple of sever traumas to the body, subsequent traumas will not significantly affect the pain being felt. In other words, after being hit a couple of times, each of the bad guys could sustain multiple hits and still not be stopped.
Both bad guys were lethally wounded early in the fight. They simply had the will to continue and did so with devastating results.
As was apparently the mantra of Platt and Matix, as should it be for all of us, "NEVER GIVE UP!" - because you can't count on the bad guys to give up.