Interesting options, I actually had to think about it for a while. Listing these in order of preference:
A) Monaco has a great location, usually nice weather and a strong vibe to the weekend. The track is very historic and characterful and has a lot of enigmatic corners (Piscine and Massenet to name two). On the downside it is very narrow and the kinks and curves make it difficult to overtake
C) Macau doesn’t have the greatest location, but the track is the best of the three in my opinion. It combines a tight and tricky monaco-style section with a wide, long, straight section of Singapore. It’s difficult to judge any more as F1 doesn’t go there (for good reason, the safety isn’t up to F1 standards).
B) Singapore has a great location and a good vibe on race weekend, but the track leaves something to be desired. It’s not the worst modern street track but it suffers from too many right-angle bends and the turn 10 chicane is an annoyance. It generally lacks the stand out features of Macau or Monaco, probably in part due to the ordered nature of the streets and in part due to the lack of elevation.