If you turn off UAC all your trusted programs run as administrator and the sort of exploits that Defence+ does not protect against (bad DLLs, macros etc run from trusted programs) will run as administrator and hit you hard. You are better protected with UAC on.
I don't see the problem with UAC. The programs I run nearly all the time run without giving a UAC prompt. I even have my limited user accounts set up so programs requiring administrator rights just do not run. I find it a minor inconvenience.