Depends - Orient Beach is much more lively - lots of goings ons. There is a section of Orient that is clothing optional - way down the end of the beach , clearly marked.
Dawn Beach is more for families, locals and condo owners go here, very nice beach. Quieter than Orient.
All of Orient Beach is considered clothing optional, and you may see nude folks anywheres, as well as topless ladies along the length of the beach. At the south end of OB is where the Club Orient Naturist Resort is located. Most of the folks in that area will be nude - and will go for walks along the entire beach. Don't worry, be happy.
My wife and I went to St. Maarten last May and loved Orient Beach. We spent the day at the clothing optional end of the beach. There is a fairly decent reef within walking distace of the shore beginning at the point where the clothing optional part of the beach begins and runs for several yards in front of the "nude" beach area. We snorkeled there for a few hours. There is a neat little bar near the dividing line of the clothing optional beach and the rest called PEDRO'S. We had an excellent burger and fries and local beer there. There was a kickin' little 3 piece Calypso band playing there for tips. So far, it has been our favorite stop.
Caymans/ Cozumel - Apr 04
St. Thomas/ St. Martin - May 05
Bahama's - Oct. 05
Western Caribbean - May 06
My wife & I also visited Orient beach. My understanding is that Club Orient is the only area clothing optional. Yet, it's not unusual to see nude people walkng the beach in the mornings. We stayed at Kakao beach which is very close to Pedro's. Nice place to stay with eating facilties, restrooms and showers. The beach is very nice. Would love to go back.
We love Cupecoy Beach. Totally clothing optional, and great atmosphere. It's a bit out of the way, but a 15 minute cab ride, through some interesting areas, and it's worth it. There are great limestone cliffs, and grottos for sunbathing, with or without clothes. A nice restaurant right on the beach steps, and all the sand, sun and surf you can stand. It was totally deserted one time we went, just us and another couple.
I went to Dawn's Beach 2 weeks ago and in May before that. It is a beautiful beach with a nice white sand and lovely waves. There is construction going on but it didn't bother me. There is food and drink also.