If I were looking for an economical way to get started, I'd probably get a pair of Cabela's mellinium revolvers, I've only shot one pair and they shot suprisingly well! I don't know why I was suprised, they are the same as the rest of the Ubertis, just not the fit and finish, but I was. I have seen a pair where the finish was removed, the brass polished and the grips refinished with an oiled finish. The result was an economical pair of pistols that shot great and looked a 100 years old. In my book, that's a hard combination to beat!
I have no experience with the 4" barrel, but I would question if the ejector would compley eject empties, which is a necessity for on the clock reloads IMOP. I have had a couple of 5 1/2" barrels, and there is some advantage to the longer sighting plane and the extra couple of ounces out front for reaquiring the target and from what I have seen seem to be the most popular barrel length. Since I don't even have the desire, much less the self-disipline to become a serious competitor, I'll forgo whatever small advantage the 5 1/2 has over the 4 3/4 cause I like the feel and and looks of the of the 4 3/4. Infact my Colts clones and RV's all now wear 4 3/4" barrels.
Having no idea of your experience's with colts or clones, I'll add this:
before you spend money on springs or action jobs, pop the grips off, remove the mainspring and from an old belt or boots cut a washer of leather to go between the mainspring and grip housing. It is amazing what this will do to improve the feel to those 10-pound-pull-lawyer-induced actions. Don't dryfire a colt or clone without snap-caps (opinion only, but shared by many). Shoot it a lot, they are pretty simple machines that just keep getting better the more you use them.
Butler Ford