Depends on the mission type itself i think.
There're various MP Mission types:
short COOP mission > real time, as it's defined by mission briefing for example
CTI-like missions > faster day/night cycles would give scenarios with long playtime more variety (but should be optional for those who don't like night missions :))
DayZ/Altis Life-like (persistent) missions > most people could just play at same time frames (due to real life), so here it could be useful to give this mission type also more variety
radical1976
