If I could have only one, the 357. Simply put even a 686 or gp100 packs better and easier than any N frame or redhawk.
I realize for carry afield many don't care however you do notice after awhile the weight and size.
Even in the same size gun It's not an easy call for me unless the appliction is something that is clearly calling for the 45 colt power level. I thought about this a bunch as I had a chance to buy a reasonable priced smith 696.
I really like the 696 however at the end of the day I could not imagine an application where I would rather have 5 of 44 special as opposed to 7 357's I carry in the 686.