Hello CXXC, you're going to have a fantastic time at Desire. You won't regret getting the passion suite either. We were there in March of this year and last. We've also been to both Hedo's a few times. The main differences are:
No singles- I had no worries if Tam wanted to party some more after I wanted to crash for the night. Didn't feel that way at Hedo. Just felt safer with all couples there.
Not as wild- kinda tame compared to Hedo II. We usually had to be the ones to get the body shots going

Not the usual in your face sex that happens at Hedo. More laid back compared to Hedo
Better food- food was great compared to Hedo being so-so. Also have 24 hr room service.
Better service- the staff was superb. Certainly not on island time. No waiting in lines at the bar because they wait on
you around the pool or beach area.
Diving- free at Hedo, pay extra at Desire.
You've got the right attitude though. Go without any expectations except having a great vacation with your love. Enjoy.
Brett