The audiences are a little different. TripAdvisor is easier to game, I find it a good guide, but there are definitely false positives. TA is very accurate for shitty restaurants.

Yelp is weird because when it's good, the reviews are great and super insightful. But you don't necessarily get a great picture of the area. (My typical use case I showing up in randomtown, USA for 24-48 hours.)