I had an early 7 1/2 and it was marvelous, but I wanted a shorter barrel, and that was before they came out with the 5 1/2" (think how long ago this was!). Even then the costs were more than I could justify, so it was sold and I moved on to a Lew Horton(?) S&W 629 44M 'Mountain Gun', then my favorite, a 624 44Spl. in 4". Wish I could have kept them all.......
So I can understand why you think a 4" would be nice, though it will still be a horse pistol more than a beltgun. I agree that when you calc. your costs in right now, then the shipping (if you must) and the barrel replacement or mods that you will be in pretty deep. If you absolutely love this particular piece, or have a bunch of work/money in mods so far (that you couldnt change over to a new one) then 'maybe', but for me the numbers dont work.
Id buy what 'I think I want' and play with both to truly decide which one to sell.