A cheek piece will be extended out from the side of the stock, pushing the sight picture towards the shoulder. If your eyes are closer to the side of your face this will be a better design for you. Stocks without a cheek piece will better fit those with eyes closer to each other between the nose.
The longer your neck, the lower you'll want the heel to be.
If you have high cheek bones, then a higher the comb will suit you best.
Then there's scope height, ring height, objective height, bolt clearance, LOP, how you use the rifle (bench, prone sitting, etc)...
To make matters more complicated...doing this at the gun store is damn near impossible because they won't mount the scope for you to get the exact fit unless you buy upfront and assemble at the store, if even then...
I believe buying a rifle or shotgun mirrors the same process for cars or mattresses - a royal PITA!
I've always heard go to the store and shoulder a few, close your eyes, etc etc., and realized I was no better off than when I walked in the door. I think the best that you could do is shoulder your buddy's rifles with scopes on them or hit the used racks with the same intents. Gun clubs might also be a better place to get a better perspective or you could drop even more coin and go get fitted (not very common for rifles, better availablity for shotguns).
With all that said good luck!