All things equal a shorter barell will have more accuracy potential due to less barrel whip(stiffness), and dwell time.......but you never know. I'd shoot the rifle in factory form first, you may find it shoots so good, that you can live the extra 3" of barrel.
I do like a compact varminter though. I took a Remington factory heavy barrel had it turned down slightly and shortend to 20" and put it on my model 7. It is my favorite field rifle for varmints. It's a .223, and yes there is some velocity loss, but things still blow up and you get used to the trajectory, similar to my 30-06.
You may want to consider a shorter factory barrel right off the go, gunsmithing isn't cheap. Maybe a pimpin little model 7 CDL, not sure if they are 20" from factory, if they are it maybe cheaper in the long run to go that route.