@Zebra 1
You'll be able to find something when travelling with the O2ptima. 2l's are usually available
O2ptima will likely travel better, especially the Choptima
iBov won't have any more jaw fatigue, the biggest thing is the face MAV's. Less chest clutter and you always know where your face is for gas addition. It also removes the ADV since it is built into the bov which is nice.
O2ptima is narrower, but it's not "narrow". You'll be fine with either unit on a boat
Both will do wreck pen comparably well, though the O2ptima is certainly more durable than the prism due to less plastic
Personal and budget preference. I like the NERDs...
Doesn't really require more attention. The SOLO board reads 1-3, and the OBOE reads 2-4 *it may actually be 1/2/4 but I can't remember and it's not that important*. None of the computers will read all 4 at once. The only unit that I'm aware of that has and displays all 4 cells is the Liberty which is also the only unit that lets you manually vote cells out which I think is really nice!