I also looked at both, but chose Major Tom for a couple of reasons. One was a couple of complaints that I read about MT canceling tours because the water was too high. I like the guy that errs on the side of safety. Also because this is a long tour and MT has great fail-safes in place to get you back to the boat - first he has extra vans on call in case there is a breakdown and second he has his own tender so if you do miss the last tender, he can take you to the ship.
Past/Future Cruises-
RCCL Sovereign of the Seas 4-day Bahamas 7/03
Disney Wonder 3-day Bahamas 8/08
RCCL Monarch of the Seas 4-day Bahamas 1/09
CCL Holiday 4-day Key West 5/09
CCL Legend 7-day Western Caribbean 9/09
RCCL Grandeur of the Seas 5-day Western Caribbean 1/10
RCCL Monarch of the Seas 4-day Bahamas 4/10