In fact you lose time by not switching teams. Unlike a geosurvey ship, there are no points that have to be collected here. Geology teams have a percentage chance of finishing which is checked each week. Higher team skill makes it more likely for them to pass the check, and the size of the body less likely. Either team could finish the survey next week, but the one with the higher skill has a higher chance of doing it. This means that the team with the higher skill will complete the job in less time, on average.