I'm a " no sightline" guy. I can use a putter with one but not having one doesn't bother me.
Been using the old Newport Tei3 the past few years and I like the clean look. I never thought of the sightlines as a guide in the past.
I'm in the process of picking up a Ping Anser 2 milled putter and it has one in the back...I'm thinking of hitting it with acetone.
U guys have a preference?