I finally got out on the course today with a sleeve of the MTB-X in yellow. I played the front nine with the MTB-X and the back 5 with the MTB Red, with the final 4 holes using a '17 TP5X and a Bridgestone E6 Soft so that I could compare.
The MTB-X definitely feels more firm than the MTB Red. Now that I have tried them side by side, I can see why some people were not a fan of the Red. The Red felt softer to me on compression, especially with irons. I liked the MTB-X much, much more than the MTB Black I tried last year. I found the MTB-X to have much less spin off of the driver than the Red and the Black. With respect to chipping, I was able to get the MTB-X to spin, but i could not quite get it to spin as much as the TP5x for some reason.
Overall, I would say that the MTB-X plays similar to the Z-Star, and given the choice, I would pick the MTB-X from this year's options. I want to give the MTB-X another round, which I may do this afternoon to compare further with the TP5X. I tend to like a softer feeling ball, and the TP5X certainly feels softer. But performance wise, I think the MTB-X may be better off the tee, but perhaps less so on wedge shots. When taking price into consideration, the MTB-X is a heck of a deal especially when bought in bulk.
I know course play is obviously what matters more than simulator numbers but ive found the MTB-X to spin more than the TP5x regarding simulators. I saw the same thing with lower driver spin on the MTB-x vs TP5x, but irons and wedges I showed higher spin with the MTB-x over TP5x (at least on full shots)... Chipping/pitching I still have to play more with the MTB-x to get a better idea. TP5x has been my ball for 2 years but this year it might be moved back to #2