The chance that they find something is independent of the other teams, so the effect is slightly worse than additive but you are probably not going to see a huge effect*. What I would do is use the 93 team (and that isn't crappy) on large worlds, and 60/50 team on asteroids or chunk moons. The only thing that skill level of the team affects is how long it takes to do the survey.
*If say T93 has a 3% chance, and T60&T50 are at 2% then the chance per turn is: 1-(0.97*0.98*.98) = 0.068 < 0.07 (that is the sum of the three teams). The thing is this includes 3 teams finding something, 2 teams finding something or just 1 team finding something. And you are loosing the fact that 3 seperate bodies could be checked simultaneously.
