RE: .17HMR or .22LR
I prefer a .22 for squirrels...I have a Remngton 541-T, topped with a Leupold Compact 3x9x33, this rig will shoot dime sized groups at 50 yards...Just never saw the need for more accuracy or range than that in the squirrel woods....That being said, my brother has a Savage bolt in .17 and he loves it as well...
I would mention, I never have liked the Ruger 10/22, seems like most guys at Rimfire Central have to trick them out to get 1/2 inch groups at 50 yards, my brother has one of them as well, about the best he can do at 50 yards is 1 1/2 inch groups....So between the 2 guns you mentioned, I would prefer the Savage.
If you don't mind spending the money, I'd look for a used 541, either T or S...One other plus to them is that the trigger is adjustable, which helps....