unity big advantage is the documentation and the java script is not a proprietary language. So if you want your game up and running I wouldn't suggest you to go with udk. There is not official support on scripting.

so yeah most people will find interesting to play with the engine great feature but in the end if you don't have a programming background it can be harsh.

But I used it and since I Don't mind getting my hand dirty it's fine for me. But I would suggest for most of people doing casual game or middle size game to go with unity. I just don't like the lack of shadowing support on the free version.