I'd say a you have a few factors to consider. What you want to see, how much you're willing to pay, and probably what kind of leisure activities you want.
If you got money to burn, go to the Maldives (I don't think there's such a place called Maldive). I haven't dived in a more expensive place than there but then again, that was before the tsunami hit. I'm not sure if the prices have come down. Despite the price, I enjoyed the dives. The variety of marine life in Maldives is awesome. Ranging from manta rays to hammerhead sharks to hundreds of parrot fish to strange jellyfish. However, the sea conditions may vary and some sites I imagine may be a little challenging for a beginner. Also, there is almost nothing to do in many resorts in Maldives, when you're not diving. So if you're there with your loved one, it will be a good bonding time.
As for Manado, don't expect to see big creatures. When I was there, the ONLY big fish I saw was a 1 m napolean wrasse. Oh yes, maybe giant clams too. And that was it. However, it's a lovely place if you like taking pictures. Nudibrach, lionfish, tunicates, and more nudibrach are order of the day. Also, diving can be really cheap there. Something like USD 40-70 for your room and 3 dives a day, per person. For nightlife, you can take a bus to town where you can sample nasi kuning, literally yellow rice. There is a couple of pubs in town too.
To get a better idea, check out some photos I took in Manado:
http://spaces.msn.com/four-engines
Look under the Manado album.
Hope this helps.
F/E