I bought a sleeve of Nike 20XI-X Balls (4.5$, 5 dots for distance) to test them. I hardly saw a difference in distance (I play with Callaway Tour i(z), 3$, 4 dots for distance). Didn't play enough to notice spin improvement.
The only noticable improvement is the slower meter. But one has to be careful. To play well and consistent, you need to play as much as possible under the same conditions. So you cannot switch continuously between the callaway (or other balls) and the those balls. So you cannot say, I will continue to play with less expensive balls and switch to those ones for important rounds. If you start to play with them, you need to always play with them, and that's expensive...
Perhaps the slower meter will help some players to ding a bit more often, but I doubt this will significantly improve the game. After a while, you will get used to the new speed and the meter will no longer look as slow as it looked when you just switched from callaway (or other balls) to the nike one. I am sure I would not ding more with them than with the callaway. But I don't want to test this hypothesis and getting used to them, they are just too expensive (for the improvement proposed).
Regards