I pronounce it the way I was taught when earning my A+ cert ten years ago, "you-fee". This is how I've always heard it pronounced by other professionals. The only time I've heard it pronounced differently is by non-professionals.
That being said, I still use the term "BIOS" when referring to "the firmware interface" for the simple fact that if you call it a UEFI and it's a BIOS, someone will smugly correct you. Other way around, nobody bats an eye.

