Both trips are great, except as Tusiops said the best diving on the Cayman Aggressor is on Little Cayman and Cayman Brac. When we went on the trip I was blissfully ignorant about how frequently the boat cannot make the crossing, we ended up making the trip but if I remember correctly it was the first time in a month that they made it. The diving o Little Cayman was phenomenal, I thought the diving on Grand Cayman was just OK, very touristy and a bit anticlimactic after LC. The Kittiwake was a nice dive, Stingray city was a novelty, but most of the other sites we did were tired and the reefs seemed worn after the pristine diving we did on Bloody Bay Wall. On the CEXII, Saba was fantastic, St. Kitts, had some nice sites and some were not so-so. At the end of the day I don't think I would roll the dice on Cayman Aggressor again due to the odds of not making the crossing. Crew in Aggressor was good, on CEXII they were great.