Each of the islands has it's own identity, but when you're there for 8 hours they're basically the same imo. I put option 2 in last place because Jamaica and Haiti are both pretty poor islands where you'll get harassed by locals much worse than the other islands to buy their crap.

I'd look at the activities available on each island and pick the one's that look the most fun to you, and choose that cruise. Again, there's not a ton of difference in excursions between the islands (lots of snorkling, shopping, beach cabana's, etc.) but some islands have unique things that may interest you. If you choose the Southern Caribbean and end up in St. Lucia, I'd recommend checking out the Pitons if you have time - that was one of my favorite excursions.