I'm a CSA bride but the wedding is still 2 months away. PM me if you have any specific questions and I'll do my best to answer them.
TA Jennifer has been to both properties and posted a great review:
Couples Swept Away, Negril, Jamaica - Site review
She would be the one to ask.
We ended up choosing CSA because it is newer and we have single guests coming and CSA is the only resort to offer double bed rooms. My understanding is that CN has a bigger pool but CSA has a large sports and fitness complex that a lot of our guests will use. I would also suggest reading the forums on the Couples site
Jamaica Resorts: Couples Resorts - All-Inclusive Resorts: Jamaican. They are very active and have a whole wedding section. Many past brides have posted reviews and pictures. A good thing about Couples in general is that they really encourage repeat business, so lots of people on the boards have been to more than one Couples property.
If you guys want to wait until June we could meet there!