I had a 28 inch creed eclips. loved it. shot lots of diff powder with 140ish bullets. sold it and bought a 24 inch tikka. found that it shoots about the same speed with similar loads but cant shoot the tac driving accuracy with the slower powders like h4831 like I could with the 28 inch.
I have a 24 inch 6.5 prc. seemed slow at first but picked up a whole bunch of speed after 200 rounds. at first it liked h1000 and retumbo. after limbering up, it likes faster stuff like h4831 and imr 4831. this is true for 140 elites, 143s and 147s. I can easily push 143s and 140s to 3150 fps if I load stiff. the 147s can comfortably go 3040ish. best accuracy in mine is around mid 2900s. this leaves room in the case not utilized which has been ok so far with es and sds. this prc is the only one I have experience with so far, and I sometimes wonder if I would benefit from a longer barrel not to gain speed, but to better utilize the slower powders to utilize case capacity. in short, I would lean toward 24 before 22.