I've got both. The 16's fun and handy as others have said, but, IMO, the 20" if you can only have one. Btw, the 16" was also "original" as a Winchester too--Pre War--as a "trapper" (an informal term, aka baby carbine, which was available back then also as special order 14" and 15"),...though they are the rarest and among the most precious of all regular (catalog) 92s with collectors--and 94s for that matter. The 16" does make a great "truck gun,".but the 20" is no slouch in that department either.
Btw, my 24" long (octagonal) rifle is the one with the 12/13 capacity, versus 10/11 for the 20" carbine (ditto 20" "short rifle") and 8/9 16"...same goes whether .357/.38 or .44 Mag/.44 Sp--or .44-40 and .45 Colt which are "magnum" length and so are 10 rd in the 20", 12 in 24".