Going down from 22" to 20" will cost you about 40 fps of velocity, but it will gain you about 10 decibels. You will notice the latter more than you will notice the former.

More bang for the buck? Then go for the 20".

Last edited by nifty-two-fifty; 12/27/16.
Nifty-250

"If you don't know where you're going, you may wind up somewhere else".
Yogi Berra