I have one AA500 in 22, the other in 177. Daystate MKIV is 22, Walther 300 Dominator is 177, so is the Anschutz 9003, and Walther LG400. Generally 22s get more shots per fill, and again generally any caliber gets iffy after 900fps. Each caliber has advantages and disadvantages. If I could have only one AA500, I would pick the 22. Neither caliber is a bad choice.
