I don't have the .44 in 16", but I do have the .45 trapper and the 18" Timber Carbine. I like the shorter bbl's, they work well in the NE hardwoods.
I have a 20" 9422, and a pre-64 .30-30 in 20", both have their merits.
I personally would buy any pistol caliber rifle in a shorter bbl, and save the 20" for rifle ctg's.
The .444 was only offered to my knowledge from Win. in the shorter bbl'd models for a few years, but the Timber Carbine with it's ported bbl. shoots so well I cannot see what adding the extra length to make 20" would do.
I believe that just as the others have said, it's a matter of aestetics.