To my understanding, the guns are the same whether .22 or .25. Perhaps adjusted differently. That's the beauty of the Avenger, it's adjustable.
Running at higher pressures isn't always your friend. The increased reg pressure can make the gun a tad more unstable (vibrate more) during the shooting cycle. I have my Impacts tuned way down, in the 110 bar range for best accuracy. Only got my Avenger a few weeks ago, and intend to use it as a slug gun. All I need to do is turn up the reg pressure and increase the hammer spring to max (about 2700 PSI and 5.5 turns on the hammer screw according to Steve at AEAC) to get max power out of the gun. Hoping to drive a 24 grain slug well over 900FPS in .22.
Might want to watch AEAC's Avenger tuning video. So, in my opinion, no, there's really no advantage to running a .22 at the higher pressures unless you have a specific reason like slugs. My experience for best accuracy for pellets is 850 to 930 ish feet per second with the pressures set as low as possible for best efficiency. Accuracy and efficiency seem to go together, at least from what I've seen.