22 Cal pellets most efficient for air ?

I am curious on the efficiency of pellet to power ratio vs air usage. So in looking at the different calibers I see the Daystate pulsar gives 250 shots at 12 FPE vs 220 shots from a .177. I have noticed a trend in shots per the same gun bust swapping out calibers with smaller changes in the 12 FPE to 20 FPE range vs .177, .22, and .25 cals. 

I have a gun with movable barrels an a adjustable regulator. Without me going through all the experiments are there any hard an fast rules on Power vs air usage in each caliber in the 15 to 20 fpe range ? I could try pushing a heavier .177 faster or try using a lighter .25 pellet with less air. I just seem to come across the .22 cal as having a really good balance between power and air usage ? BTW i am not a .22 fan, i kind of dislike the caliber.

I guess I am looking as setting up a gun with 15 to 20 fpe with the most shot count and accuracy being the same in comparison between all 3 calibers.
Seems like the air used to push the .177 pellet past 850 fps become inefficient. The mass of the .25 seems to use more air but once it gets moving you get alot more power. 

So anybody have any thoughts ?