My first choice will always be Couples Negril. We honeymooned there for 10 days back in October 2005 and it was HEAVENLY!
Our awesome Garden Suite, the lush grounds, the gorgeous beach with calm crystal clear water, the amazing food, the artsy tropical decor, the wonderful staff, and of course the fantastic STRONG drinks all made it the trip of a lifetime.
In my opinion, Couples includes much more for your $$$ than Sandals (scuba, off-site excursions, etc.) Plus, Sandals sometimes costs more than Couples depending on the time of year, etc. Sandals kinda has a "cheesy commercial" quality to it that turns me off. Couples is sooooooooo not commercial. Yes, its an all-inclusive resort, but you feel like you truly get a sense of JAMAICA when you stay there. That being said, I would definitely leave the resort grounds, contact Sala and Sienna of Talk of the Town Tours, and head up into the mountains to Benji's Paradise!!
Also, even if you don't end up choosing Couples, I highly recommend staying in Negril vs Ocho Rios or Montego Bay. I've been to Jamaica four times and, to me, Negril just feels right - very mellow, stunning sunsets, not terribly far from the airport, gorgeous beaches, and not too crowded, etc. Ocho and MoBay are both loaded with tourists since Ocho is where all the cruise ships come in and MoBay is where the airport is.
Negril all the way mon :-)