I am very late on the discussion, but i like them equally. The ending from gravity falls is a lot better, but considering all the scope of the series; it has a LOT of weird fillers... I like them, but otgw just have one filler episode, so i think both are equally good. Over the garden wall mastered what it could do with the time it had, but doesn't have a very detailed plot. Gravity falls didn't mastered but has an AMAZING plot history on my opinion.