Stayed almost everywhere in Jamaica. Between MB and Negril, I wouldn't even have to think about it for more than a second. I can honestly say that everything about Negril was better. You can catch a hop flight from MB to Negril, did that our 2nd trip there. It was a little pricey, but worth the time saved IMO. Here's why...the cab/limo ride from MB to Negril will remind you that you are in a nation with high poverty. The road conditions are horrible, and barely wide enough for two full size vehicles. Add to that, every driver truly believes they own the road. A/C is rare in vehicles, because they are used to it. You'll see a lot of bare footed folks, women carrying goats over the shoulders, kids asking for money/food/candy anything at stops.
It's not ALL bad though. As long as you know where you are, enjoy it. See the country for what it is. All of the children in the school uniforms (which are the color of the grade they are in, and what trade they are pursuing). Shacks on one side of the road, and amazing houses on the other side. Stop at some of the local restaurants, the food there is infinitely better than what you will get at a resort (which is still very good).
If it is your first time to Jamaica, definitely make the drive from MB to Negril, and absorb the culture and way of life of the people there.