There were very good players that swore these cb changed from table to table, measle to red circle etc. I think it was mostly mental myself. I considered myself pretty sensitive to this stuff, and in hard times for example the cue balls played very consistently table to table, no matter the color of the dots on it. The one place I definitely did notice a difference, just for a reference point, was a place like on cue in san diego. The cb's played so light!! I asked somebody there once, and the guy told me he didn't think they had changed the cb's in a very long time (ie 10 or more years). These are the situations where the cb really is playing strange.
I think it is mostly mental. Of course the weights do vary slightly from one ball to another, but I don't think the % change is even worthy of attention. It gets a little damp and a guy thinks it is the cb, but it is the cloth. Imo, even in the case that it is the cb, you aren't really playing any differently anyway. For example, if you feel you are playing with a heavy cb, you will need to adjust your billiards or draw more, or whatever it is, same as you would with damper cloth, so what is the use in worrying about it. I suppose you would need to adjust when compensating for deflection on a heavy vs light cb, but this is done subconciously anyway; there's no way you are going to say "this cb is light i need to cut it 2mm more".... you will just start to feel it. So, why worry about it.
Anyway, long story short, I just don't think cb's vary too much in good rooms with brunswick centennials and the rest of the high quality balls. And even if they do, you just need to adjust to them as if you would anything else. I feel way too much thinking goes into this. You see guys arguing over which cb to play with and it is a joke; it mostly has to do with what ball the guy has hit a million balls with in his home room and is more comfortable with. The desired cb in effect turns into a kind of coddling "blanky" fetish much like that of a young child's. Do your game a favor and forget it all (not talking to anybody in particular, but I honestly believe it is good advice).