We've been to both, and I guess it all depends on what you're looking for. You'll find people on the board who CSS is their fave, and also people who CSA is their fave. We've been to both, and CSA is our fave...
If the beach is important to you, then CSA is the way to go. CSA's beach is soft, white sand. CSS's beach is rocky sand, and very small. However, if AN is important to you, then CSS is the way to go - as that is not an option at CSA.
I do like the room service dinner option at CSS (not available at CSA).
If you're interested in working out at all while you're there, then CSA wins hands down. The workout facility is pretty amazing. CSS's is very standard, like a typical hotel workout room.
We preferred the food at CSA, possibly because there are more "healthy" options available than at CSS.
We also preferred the layout of the resort at CSA. It's flat, spread out, while at CSS, there are many stairs to contend with. Then again, we were in a beachfront room, which is the lowest part of the resort, and if you want to go to the restaurants or bars at the top of the resort, it's quite a hike. Or if you go up there and have a few too many drinks, ahem, not that that EVER happened to me.. but you may find the stairs a challenge on your way back to your room (if you're beachfront).
If doing Dunn's River Falls is important to you, then CSS is the one to pick. DRF is right up the street from CSS and is also an included excursion. If you went from CSA, it would be a 2-3 hour drive each way, which would probably take up most of your day.
And I don't know if it's just the time of year we've visited the Ochi side of the island, but it seems like we've always had better weather in general in Negril. We could have just lucked out, because I know the weather has to get bad in Negril also, but for us, we've always had more days with blue skies in Negril. You will get a typical afternoon shower in Negril, which lasts maybe an hour, then the skies will open up and you'll enjoy a beautiful sunset. Last year when we did the CSS/CSA split, the only truly sunny day we had at CSS was the first day we arrived. We didn't even get a tan until we got over to CSA. We've also been to another resort on the Ochi side several times and experienced the same thing with the weather. Again, it could have just been the timing for us.....
If you have the time, you could always book a split. Couples will transfer you to the second resort with no additional charge (aside from tipping your driver). Only do this if you have enough time to spend at each. I think we did 4 nights at CSS and 5 nights at CSA.
Hope you find this helpful. There is a review of our split between CSS/CSA somewhere on this page (you may be able to find it by searching CSS/CSA split, not sure) that also has a lot of comparisons to CN since we'd been there before.
Melea & Joseph
CN - '06, '07, '08
CSS and CSA - '09
CSA - '10