I carry both frequently. Most typically my SP101 but last year I bought Taurus Mil Pro .45 that almost fits in the same envelope so I can pocket carry it if my pants are loose enough.

I tend to the .357 when I'm out somewhere the shots might get long (or just in a revolver mood which is most of the time).

I lean to the .45 when I'll be in close quarters and/or low light. Situations where the .357s flash and blast are negatives. I can also reload the bottom feeder faster than the revolver (rarely a concern in a typical self defense situation). I also lean to the mass=penetration theory and prefer the .45 when the weather gets cold and clothing gets thick. You also have the bonus of it being a big hole should clothing cause a failure to expand.

These are not hard and fast rules and I'll swap either in to the other's situation out of convienience or necessity.

I'm very blessed to have a wide and diverse set of carry options. I have a pocket .380 for when I need to be really discrete or the weather here in the South gets really sticky. I also own several high-cap 9s now and carry them from time to time. I even own full size service .45s and .357s that might get carried from time to time.