Well this is obviously stressing you out thinking you'd rather go to CSA. I'd suggest you go ahead and change to CSA since it looks like it's pulling you more than CTI. You can still do the horseback riding at CSA, but it is not included and will cost you extra. The cat cruise at CSA is really amazing because it takes you to a cave where you get out and swim through, where CTI just goes down the coast, lets you swim and takes you back. But CTI does have the island where you can sunbathe au natural. CSA has the very romantic Atrium rooms with a hammock for two.
My advice is to step back, listen to your gut and then let it go and stick with your decision after that. But at this point, it seems CSA may be calling to you more, so I'd book that and then stick with it. Go to CTI the next time to experience the other side of the island. Then you won't stress out about your decision because you've already tried CSA and then can be comfortable trying CTI. Trust me, after you have been to any Couples, you'll definitely be planning a trip back.