The amount that your limit break meter goes up is a function of how much damage you take and what limit level you're currently set at, and some specific status effects.
I know that the higher the limit level, the slower the meter increases. The question is just how much slower does it increase with increased limit level?
One thing to look at, for example, is Yuffie's Bloodfest (level 2 limit break) vs. Doom of the Living (level 3 limit break), which have similar mechanics. Although Doom of the Living will deal more damage than Bloodfest on a single use, the fact that I get to use Bloodfest more often might outweigh that overall. I can't be sure unless I know how much the limit level affects how often I get a limit break.
What are the specific mathematical mechanics for how the limit break meter increases?