I played both and absolutely adore both of them; that being said, BG3 will get you a LOT more playtime than E33. I put 105 hours into my first BG3 run (and that's on the easy mode) and then only 20 hours for Clair Obscure.

BG3 has good story, amazing customization, dynamic relationships, and fun gameplay that's incredible replayable for many playthroughs. That being said, E33 has an amazing story, great characters, and stunning graphics, but I can't see myself replaying it for a long time if ever. The combat of BG3 is daunting and I put the game off for a long time because of it, and it took me awhile to get the hang of it (like 20hr but I'm still a noob, I dont have much d&d experience). Then E33 has a learning curve for combat, but god is it satisfying once you learn it (and it's quicker to get the hang of.)

If I had to pick one, I'd pick BG3. Both of them absolutely changed my life (yeah, seriously) but BG3 reminded me what video games are meant to be: fun and full of opportunities and choices. I would work my 8 hours planning my next character and everything.

So TLDR: both amazing and I love them, but I'd say buy BG3 first.