This is measured in everything from the look, length or head design of the club. The best thing when looking at putters is to find one that looks the most comfortable when setting up to it. The look boils down to creating a sense of confidence. Anyone who's ever picked up the sticks will tell you confidence is vital in striking a ball correctly. But if you're overly confident, sometimes the ball can come off the putter too hard.
Inserts give more options on feel.
Ah yes, the insert. The hottest thing going in the world of putters. The premise of inserts is a plug, made of polymer, plastic, rubber, urethane or whatever substance the lab gurus come up with, that is placed in the face of the putter head. It makes for softer contact with the ball upon impact, resulting in the hoped-for effect of truer roll. As far as inserts go, I've tried a few of them, but I feel the consistency of my putter from 1988 is as good, with no insert, and the ball doesn't jump off the face.