Hey
llllllll,
I have a few questions. What kind of filter do you have? How big is the tank? And how many fish and what kind are in it?
I see you said you bought 15 pounds of ceramic rings, I'm going to take somewhat of a safe guess here and say you probably have enough. Also to answer your original question, it probably won't make a noticeable difference as far as the big ceramic rings or the small ceramic rings. Whichever choice you went with should be fine.
Also the guy who told you sintered glass or matrix glass is better, chances are even if that were true its not so much better that it would make any kind of real difference. Stick with what you already bought.