I've only ever used Fuzzibunz & BumGenius. I have a couple of kawaii's (not a fan, they've never fit Connor well), and I recently got a couple of Oh Katy's (they are pretty good).
A few weeks ago I decided to try the alva's because I heard such good reviews and they are SOOO cheap! I ordered girl patterns for the new baby, but tried them out on Connor (ssshh don't tell Daddy he's wearing pink flower diapers! LOL

) and so far I haven't noticed much of a difference either.
I would venture to guess they are so much cheaper, not just because they are made overseas, but they probably won't last as long? Just a guess! I've had my original stash of FBs and BGs for 2.5 years now and they are just now starting to show signs of wear (but not effecting the use of them), so I'm guessing the cheapies won't last as long and would need to be replaced sooner.
I love my OS pockets, I've never used anything else. We started CD'ing Connor when he was 6 months, so didn't have to worry about sized diapers with a newborn. However, he was born 8+ lbs and I expect this girl will be closer to 9lbs so I plan on sticking it out with the OS dipes!