We spent about three weeks on North Sulawesi islands a couple of months ago, staying at Bunaken Oasis, Murex Bangka, and Lembeh Resort.
The Bunaken diving is virtually all walls. Nice, healthy walls, of course, and many turtles. Bangka has some wild topography; canyons, swim-throughs, etc. We dove three days at Bangka and it wasn't enough; a week at Bunaken and it was enough diving, but not too much; and a week at Lembeh, which was barely enough but we saw all (well, many of) the things.
You likely know that in Lembeh, there is very little to do besides dive, and there is nothing to dive except muck, with a few interesting reefs. At LR, there is excellent food, lovely rooms, a nice pool, and a well-operated dive op. Bunaken Oasis is a jewel--gorgeous, large pool; remarkable restaurant, lovely cottages; very nice day boats--really, the entire package. And at all three, the staffs are terrific.
Because we did not stay at Murex Manado, we didn't qualify for the "Passport to Paradise," which is exclusive to the three Murex operations (Manado and Bangka are owned by the same family, who really opened up North Sulewesi diving; they also own the dive concession at LR). Nonetheless, we did have day boat transfers from Oasis to Bangka and Bangka to LR. We did not dive between Bunaken and Bangka, because the Ruang volcano erupted in the wee hours and things were dark and ashy; we dove twice between Bangka and LR, and it was great.
We agree that the three types of diving, and the quality of the resorts and their dive ops, makes North Sulewesi a great destination, and are already scheming a return. Not that you asked, but
here's a batch of images from the three locations.