Hmm, there are exceptions, but I'd break it up this way in general:
balmoral shoe > balmoral boot > double monk strap > blucher shoe > blucher boot > single monk strap > loafer
The shoes to boots formality is for the same style. For example, though shoes are more formal than boots in general, a no brogue cap toe blucher boot is more formal than a long wing. There might also be some single monks that are more formal than bluchers, and some bluchers that are more formal than some double monks, but I think the trend is as above.
Anyway, specially for bluchers (shoes and boots), I'd say (bicycle toe not considered):
no brogue cap toe > perf cap toe & plain toe > half brogue cap toe > split toe / NST > long wing & full brogue / short wing
I'd like to hear other comments though.