I used the Callaway Tour i(s) for months and they are a very good ball, I probably agree the best for the price, I may even switch back soon. The reason I tried the NIkes was sometimes the Callaways seemd to have a mind of their own and they would wander WAY off for no apparent reason, (apart from the VEM) and the slower meter speed seemed at best, variable.
So a few weeks ago I bought the Nike 20XI-s balls and I love them, I'm now on my third sleeve and they are getting a bit pricey.
The difference with my club set is marked, and I accept some of this may be psychological, but:
Distance about the same except with spin
Spin, a lot more spin on the Nikes but when used it does cut the distance by a good 3 - 7 yards.
Precision, the Nikes go where I put them, much more precise.
Putting, I don't understand this myself, but my putting with the NIkes is significantly better, those putts I used to miss by an inch now go in and heck sometimes even those ones where me and the ding are in the divorce courts, (you know, the ones you think will go sideways) even go in. It was the putting that persuaded me to buy the second (and third) sleeve.