We have actually stayed at both places and I would recommend both definitely.
Both great locations, both have great staff and Negril Escape is Jamaican family owned

However I never stayed in one of the rooms with a kitchen at Xtabi, I have only stayed in the superior rooms but was more than pleased with them.
At Negril Escape I stayed in Jamrock in one of the two room suites with kitchen. There was more than enough room. A closet and a dresser. I have also seen the inside of many rooms there and they all seem pretty nice.
The breakfast at Negril Escape is a buffet if they have multiple people staying there. If not, then you just order whatever you want off the menu.
I would say they both have pretty good snorkeling, Negril escape might be just a bit better and of course you have the lighthouse to jump from (if you dare) lol
I would say the food and bar is better at Xtabi

Both are pretty good choices, I don't think you can go wrong!