newone203,
Barrel length is not the best indicator of accuracy. nmleon is correct that a shorter barrel tends to be stiffer thus inherently more accurate but an accurate barrel usually comes down to the quality of the rifling.
As for velocity, there’s not much to be gained past 20” unless you’re shooting something chambered in one of the WSSM calibers and even then about 22” is all you need to realize maximum velocity. I tend to focus more on the intended use of the weapon.
For chasing jackrabbits thru the sage brush I tend more towards a light weight fast swinging 16” barrel that I can pack all day and not tire. I give up just a little velocity but most of my shots will be close.
When calling coyotes from a stand I don’t mind a little extra weight since I’ll be doing a lot of sitting and usually pack a heavy accurate 20” ultra match barrel. Shooting from a bench, who cares how heavy or long, it just has to be accurate.
Hope this helps.
Joel.