From what i've seen, all the leaves drop saplings at the exact same rate, not accounting for the amount of leaves blocks a given tree will have. For example, it's not rare to get less than 4 grimwood saplings from chopping down a single grimwood tree and to not get a sapling from a laurel tree if the short variation ends up spawning

I'll buff Grimwoods since its rare but you still definitely get a good amount plus the rates are affected by Fortune. Laurel will stay the same since its whole biome generates and the leaves generally have just a bit less than the typical Oak.