Atlantis Sub vs. Ocean Explorer

[Grendel]

We were thinking about doing one of these when were at cozumel. For the most part we want to relax and hang out but one of these seemed like a nice diversion. I realize the Sub actually goes under water etc. But is it really that much better than taking the Semi-Sub? Plus the ocean explorer excursion is shorter which leaves that much more time.

also are they equivalent in terms of being cramed in like sardines..or do you have more room in the Ocean Explorer?