This topic is somewhat actual for me. If I simplify, I think we can say that the most used balls in CR are the Joola Flash and the Joola Prime, and the opinions on the balls can be very very strong. In the higher leagues, the Prime is used and noone uses Flash, whereas in the lower leagues people prefer the Flash. But I am mostly writing this because we had a lot of fun with this topic. E.g. in Policka meeting 70% of people voted for Flash, we played with Flash, and some higher level players in desperation occassionaly uttered things like "f... bakelite" etc.
Also, my friends from another team, using Prime, make fun of me, because we use Flash, and they say jokingly that with our members style/type of play, that is actually the only chance for us to be able to stay in our level, called "divize" in CR. And once, when our team voted what to use, it was close. Then I told my friends from another team, in a kind of hopeful mood: "See, I think we'll make one last season with Flash and then...", and they replied: "No, no, no, Honza, all seasons, all seasons... OK, get a bit back to reality, all seasons..." ;-)