A.M.
We use the Bumgenious(onesize pockets) and Fuzzibunz(pocket). Our son is 24 lbs and is in the size medium Fuzzibunz(new style) and still has room to grow. The only disadvantage to the Bumgenious is that my son can now un-do the velcro fasteners. We love them both. We sometimes double stuff them if we know he will be wearing them for a long time (long naps) and have no issues with leaking. I do suggest getting the rice paper liners. They are a flushable liners that you can use. It makes it so much easier to flush the poop out.
Good luck doing your research and making your decision!