We have been to Bintan twice. Went there last weekend (highly recommend)
We stayed at Bintan Lagoon (nice) and last weekend we stayed at Niwanna (excellent)
Nirwanna is more conventient for beach as Bintan Lagoon is very hilly.
The service at both places are wonderful. The beach at both places are sandy (not coral). We stayed in a Suite (1148) looks at beach and beach only 20m away from door. Room was so big and beautiful.
I book on the Nirwanna website and booked ferry on their website. I had done alot of research on prices and found to be cheaper direct. Also I do alot of hotel booking with www.wotif.com
The food was much nicer at Nirwanna
Hope you have a great time