The OP should be able to run Standard Velocity CCI in both without problem. There is no need to run the more expensive ammo in his pistol, that's up to him.
Even the high velocity ammo like CCI MiniMags will stay subsonic from the short P22 barrel. The CCI subsonic are a bit oversized and will not chamber well in the 10-22 if it has a match chamber.
I like Winchester Dynapoints as a general purpose std. velocity ammo without being crazy expensive.
Remington Subsonic is horrible ammo, avoid.
PMC Moderators very quiet but too weak to cycle.
Any of the std. velocity loads should work in both.
I'm sold on Blazer for the short pistol barrels. It is cheap, reliable and has a low stdev. I have not seen it on my chronograph, but about 1% of them go supersonic. I use CCi standard velocity for the rifles.