Lust epidemic is easily one of the best ero games ever made. The mechanics and exploration are fun and the hint system is perfectly designed so you never get stuck.
Treasure of Nadia by contrast has way better animation but it feels TOO big to me. In contrast to Lust Epidemic, there are too many characters and too many things to get through before you get the scenes you're looking forward to. That being said, it's still just as streamlined, and the quality is great there's just a lot to do and it gets in its own way, especially with the money grinding mechanic.
Lust Epidemic feels must more focused and it made for a better experience to me.