I definitely enjoyed the BG2 story more, but their both fun. I guess it largely depends on what's your personal preference. BG2 was made in the 90s and has a 90s style D&D atmosphere. BG2 is real time turn based. You don't make every single move for each character. It's somewhat automated. I prefer the BG2 classes and Forgotten Realms setting. I grew up reading the books.

Divinity Original Sin is fully turn based and has a very different setting. The characters are a lot different in style. The classes are vastly different. The game is turn fully based. There is much more micromanagement. It's 3d vs the 2d of BG2. I'd say it's much more balanced in terms of class power if you care about that. i thought a lot of the voices/dialogue were a bit annoying, but could be fun sometimes. I definitely didn't like the classes as much, but I'll admit there is much more room for customization. It also has crafting which I'm not a big fan of. BG2 has crafting of a sort, but it's mostly for unique items made from unique items.