The general thing I personally keep hearing is both are better than what most average critics say. Birds of Prey is being called one of the better DC movies as it focuses more on just having fun with itself so it's almost like an R-rated Shazam (the "radical feminist" stuff some people on social media keep claiming is more from the bad side of the movie's fanbase, apparently the movie itself really doesn't feel like it's trying to beat people over the head with a "woke bat"), while Sonic is a fun family movie that fans of the games young and old can enjoy.
I've seen people who enjoyed both like Critikal, and of course you shouldn't lump every Birds of Prey fan in with the bad apples (for one Vivziepop of Hazbin Hotel fame said she loves Birds of Prey, and it would be stupid for people to suddenly start hating Hazbin Hotel and Helluva Boss just because she likes a generally harmless comic book movie).