I went through K-1 visa process 15 years ago. So please treat my response with a grain of salt.
I would say that either K-1 or I-129F are much safer than UFU program. Because that's a straight path to green card and citizenship, while under UFU it's not at all clear. With K-1, you'd have to apply for your fiance and wait for her to be approved overseas. 15 years ago that took a year.
Under I-129F, she/he can enter US right away and can wait for AOS in the country.
But my main recommendation is to pay a couple of hundred of $$$ to a good immigration lawyer for a consultation. Filling out paperwork is easy on your own, but knowing which path to take is worth spending the money on the lawyer.