I was in Curaco in 1999, at a place then called Princess Beach Resort/Princess Beach Divers. It was terrible, the dive op was a joke, and the sites were very average. This past February, I visited Sunset Waters Beach Resort and found this all-inclusive resort to be a fun and relaxing place, the dive op excellent, and the dive sites among some of the best I've been to.
I've been to Bonaire twice and stayed at the Plaza Resort both times. I dove with their in-house dive op. The first time was fantastic, dive op was super and the choice of sites top notch. The second time around was not as good...very crowded with a more limited choice of sites.
Bonaire has a much more developed system of shore diving with lots of well marked sites, reasonable access, and maps. Curacao has much fewer shore entry sites and they are not as well marked. If you expect to be boat diving for most of the time, this won't be an issue. Both islands have central towns that offer restaurants and shopping, but Willemstaad is actually a little city with a decidedly Dutch flavor. Personally I prefer Kralindijk, although Willemstaad is more scenic and has some interesting historic sites. Kralindijk has some of the best little restaurants I've come across in my Caribbean travels. It has a much less cosmopolitan and more laid back feel to it which, to me, makes it a more relaxing place to hang out. People in Bonaire seem a little friendlier and less stressed than Curacao, although that's just an impression of mine.
My first trip to Bonaire and my last trip to Curacao were both exceptional. I think your results will depend on where you stay and which sites you dive. Both have some superb, as well as some very pedestrian, diving available. Both also have some really good shore diving and even snorkeling sites. Beaches are limited, so if you want to see some white sand you'll have to pick your destination very carefully. I can recommend the Plaza on Bonaire IF you want a beach, a good on site house reef, and don't mind a larger resort and dive op. On Curacao, I was very impressed with the Sunset Waters Beach Resort. Nice beach, good food, excellent house reef, and well above average dive op with very personalized service. I can recommend it IF you want a beach and don't mind being a bit isolated and a 30 minute drive away from town. (The resort does offer free shuttle service).
Writing this reply to your post has brought a smile to my face. I have wonderful memories of both places and would gladly go back to either location. You'll have a wonderful time and can not make a bad choice.
Stan