I have both and really like the shorter one better...and here's the reason. Living on a small farm here in KY, I find that the shorter one slips nicely into a rear jeans pocket for carry while I'm doing chores around the place...and with complete security too. The 5-1/2" will not do that...the barrel is just too long for security without a holster.
That shorter barreled model is so convenient, that I'm rarely outside without it. The shorter barrel allows me to dispense with a gunbelt and/or holster. The result is I'm with the gun a lot more...and that translates to familiarity and more shooting. (Even in the wilds of KY, you just never know when you'll get p-----d off at some errant knot hole or thistle top.)
The 5-1/2", as Dale 53 said, is a little more accurate, more muzzle heavy; so it does 'hang' better out there in offhand work. Accuracy wise, shooting from my favored back rest position with the piece extended between my up-raised knees, I find them identical.
Throats are both at .432", and exhibit no leading at my customary loading velocities...~1000 fps. 240 gr Cast Keith type SWC's with Skelton's favored load of 7.5 gr of Unique will do that speed in my guns...and is my go to load..but it can also be duplicated by 7.2 gr of either HP-38 or Win 231. Both guns like 6.0 gr with both of those two last powders, giving me close to 1" gps at 25 yds with 750 fps chrono'd velocity however. The Skelton load is a sub 2" prescription.
Were it me, I'd opt for the shorter bbl, but it's a personal preference based on portability without a holster.
Regards, Rodfac