With a cartridge this big, longer is pretty much the way to go...especially if you plan to shoot full house ammo through it. But actually if you throttle back slightly with the big magnum pistols you could do very nicely with the shorter bbl. They are faster, easier and handier to carry and use. And these are pretty important issues IMHO. My first few pistols were all 4" bbls and I shot a zillion rounds through them and just got used to that length and feel. Actually I've found I don't shoot any better or more accurately with longer barrels.

If you get the shorter bbl, try something like 19grs of 2400 behind a 215 gr bullet and I think you'll fall in love with it.