In contrast with the other answers, I'm going to say that oil-based paint is not the answer, and in fact will often make the problem worse.
If you are getting mold, the issue is quite simply insufficient ventilation; You need to improve it by either getting a higher cfm exhaust fan, running it for longer, or fixing any other issue (blockage / vent location etc.) there is with the current setup.
If you use an oil-based paint, should you get any condensation, it will bead on the surface, and if not allowed to dry properly (due to the poor ventilation), this will allow mold to form. If you use a (porous) latex paint, if any condensation happens, it will simply be absorbed. If ventilation is poor, then this damp will also build up over time and cause mold. The thing is, that this will happen more slowly, because the surface moisture level will actually have longer to build up than than for a non-porous surface, allowing longer for the poor ventilation to actually dry things out.
Sure, it wipes off more easily from a shiny surface, but the trick is not to allow the mold to form in the first place.
I know people will disagree with me here, but in over 30 years of home ownership and four different bathrooms, the only time I have ever had ceiling mold is when I used an oil-based primer over some caulk before painting the whole with a latex-based paint; You could clearly see where it was by the black marks - the rest of the ceiling was completely mold-free.
Oil-based paints should only be used if there is no chance of achieving proper ventilation, and the only solution is regular wiping-down.