Good points, but one thing I'd like to add is if you can pick a putter that's available in a variety of plastics, that's even better. Star / Champ / Evo / Z etc. can be nice for a driving putter that might take a few tree hits per round, while baseline or soft baseline plastics tend to be superior for putting putters.
Also when you find the mold you want, try out a couple of different weights too.
The secret strength of Gateway putters.