boot fitting question - shim vs. heel lift

One of my boots is a little loose in the heel and I'm trying to figure out if I should put a full length shim under the footbed or just put a heel lift. I tried putting a heel wrap on and trimming it, but this is really overkill and ends up pinching regardless of how much I take off. It feels like if I get just a little bit under my heel, it will fit better in the pocket and the problems should go away.

My heistation with the heel lift is that the other boot fits really well. I don't want to lift one heel and not on the other. I figured that if I put an insole shim (probably just start with 1/16"), this would probably be better because it's keeping my foot/leg at the same angle as my other boot. Is my thinking correct?

thin heel lift in both boots