Our experience and testing has told us that MOI, along with having the right loft for your stroke, are the two main factors in putter performance. We have not seen much of an effect from face treatments, either materials or different milling patterns. You have to be careful watching videos or slow mo illustrating how a ball rolls off of a certain putter because it is very easy to manipulate the video to make it appear there is a major effect. I’m not saying anyone purposely would do that, hopefully not, but some that I have seen are questionable, in my opinion. I would only trust results we were able to get through our own testing. We have tested variable milling patterns on the face to determine if the roll on off center hits could be improved and the results were negligible on the patterns we tested and difficult to conclude any variation was due to the milling. Of course, there are a million variations of face patterns, materials, etc. that are possible. To date, any we have tested have not produced “Wow” results. The most important aspect of the face is that it is flat (that is really why CNC milling is used, to insure face flatness, at least for us) which is the key factor in producing consistent roll. MOI is important because the higher it is, the more stable the head is. What number is high enough? Hard to say, but the Moment X is plenty high. We know, through our testing, that when comparing a putter head with a about a 4500 MOI (25 ou/in2) vs a 8500 MOI (47 ou/in2) there is noticeable difference in the distance (and to a lesser degree the direction) on off center hits of 3/4″ toe and heel. Noticeable difference being 2″ to 4″ approximately on a 22 foot putt. That is enough to make a difference and enough to sometimes mean missing or making a putt. Much more difficult, again in our testing, to see that much difference between the 8500 MOI and the 10000 MOI. My guess is 10000 to 20000 would not be noticeable, but that is just my guess. One point to make, putts hit on center, MOI has no effect on how the ball rolls.
Lastly, having the proper loft for your stroke is very important to getting the best roll. I think this is often overlooked. Loft (and your stroke) are the major factors in how quickly the ball starts rolling. NO putter produces immediate roll. Those that claim it are not being truthful. We have tested negative lofts, rounded faces, etc. and there is always a bit of skid, then tumble and skid, then roll. Ralph determined years ago that 3-4 degrees of loft, generally speaking, is the best loft range to get the ball up and on top of the grass, minimize the amount of backward rotation and skid, and get to the true roll condition.