I have owned a variety of SAAs over the years, and generally prefer the 7 1/2" in .45 or .44, and the 4 3/4" in .38 & .357. I don't particularly like the 5 1/2" in any caliber. That said, since you aren't planning on carrying your SAA, I'd go for the 7 1/2" barrel if for no other reason, it just looks "right".

Life is hard. It's even harder when you're stupid. --John Wayne