The putter grip is often an enigma. It seems many golfers either run with what came on the putter or choose based on comfort. Online fitting tools have become quite popular recently and some can offer pretty good guidance.
Super Stroke has their grip fitting tool available and after answering a few simple questions regarding your stroke and tendencies, they recommend an option best suited for you.
The Super Stroke grip fitting tool features 4 simple questions and then below it offers some of their selections. You can even toggle between some of the questions/answers to see how it changes their recommendations in real time.
Give it a try and let us know below which grip options it recommended. You can find it on their website here.