I always prefer coordinates in latlon WGS84 because they are usable worldwide and easy to understand once you know which is latitude and which is longitude.
I happe to live in a country that has several UTM zones, and before that several smaller Gauss-Krueger zones. As long as you are within one zone, everything is ok, but cross-zone computing always leads to trouble.
Apart from that, many old projected CRS have datum shifts of up to hundred meter. WGS84 is on the safe side to avoid additional datum shift misunderstanding. Unfortunately, some countries had adopted UTM with different datums before WGS84 was established. So you have to ask for UTM zone, ellipsoid and datum.