Download WOTLK VS WOTLK (Old)

Hello there, i've been experiencing some game freezes lately and i really dont know what to do besides download the game again, but my question is.. What's the difference between wotlk and woltk(old)? I can see 2 versions of wotlk but idk which one i should go for :(

Go with the old one, it's the clean default client.
The new one has WOD models and it's know to have some issues.