Desu or Uguu?

[Jolt]

Uguu is much less annoying, thus it had my vote.

[Koga No Goshi]

Desu is almost never actually used outside of business or semi-formal situations such as speaking to a boss or older member of someone else's family. I guess the train and bus announcers use it too, but that's basically business.

I honestly don't know why it crops up in anime so much. It's one of those mysteries like villains calling themselves "oresama" which is super arrogant and unrealistic in real speech.