In a "street fight" scenario as discussed here, IMHO, I'm with Jeff Cooper. Far more important than "how many" rounds of .38 (actually .36) can I carry in reasonable comfort, is confident shot placement and combat/survival attitude.
I grew up as an aerial power lineman which requires extensive ropesmanship. You must rig, lift and move things with ropes and knots. A very temporary and weak knot is a half-hitch. The saying goes "13 half hitches will hold anything, but one of the correct knot, will work far better".
The .45acp is a proven fight stopper. If you are in a fight that requires more than seven rounds of .45acp, especially with the exotic ammunition now available to us, you need to be using that "purpose built" defense handgun to fight your way to your long gun, presumably in your vehicle. For carry, Colt's Lightweight Defender is hard to beat. I have one equipped with a Chainmail Crimson Trace laser and it affords absolute confidence. Those who would say that a self loading handgun can malfunction, are correct - any firearm can. But, the 2000 rounds you put through it to gain that confident shot placement and attitude will expose weaknesses and give you an opptuity to correct any problem a thousand rounds before your life depends on it.
Anyone who has not read Jeff Cooper's books: "Principles of Personal Defense" & "To Ride, Shoot Straight and Speak the Truth", I highly recommend it. He is, after all, the father of self defense & handgun craft. Just my 2 cents, and worth every penny.

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Jeb