I don't feel like playing the game in both languages just to check the differences myself.
Is there any special change in dialogue with NPC's between those two languages? Or is it just different spelling of certain words?
If someone could provide screenshots of same part of the dialogue with any NPC on both languages that would be good too.
Best Answer
UnEnglish is the original English translation done for the game. As you might know, the creator of the game is from Spain, and English is not his first language. That's why the quality of that initial translation is not so good, in terms of grammar and vocabulary. After the game started gaining popularity, the original translation was corrected by a native English speaker, as can be seen in the "About" section:
The original English translation remained as UnEnglish, just for fun.
The main differences between both translations can be found at the very beggining, and I grabbed some screenshots to show them:
Conclusion: UnEnglish version should only be played out of curiosity, but it will mostly look like crappy English for the ones who can speak proper English, and more geek references means more fun, so go for the English version.