OOOhhh - pages of opinions
Generally speaking I test my springers with a light - AA Express, a medium - JSB Exact, and a heavy pellet - JSB Heavies. Invariably it's the lighter pellet which produces most power in a springer, typically the opposite of a PCP incidentally, so I use AA Express to set them up for power.
That being said, I'm not looking for mid 11s like I would be in a PCP, springers usually shoot more accurately and feel nicer with less recoil, so high 10s, low 11s are where I want to be depending on the gun, it's a balance of feel and power, not just power on it's own