Well I just came back from 2 weeks in North Sulawesi - 5 nights / 18 dives at Lembeh, 5 nights / 17 dives at Bangka, and 2 nights / 2 dives at Bunekan. If I were to do it again I would just go Lembeh and Bangka.
Lembeh is quite specialised if you've never tried muck diving before or if you don't enjoy macro you should either skip it or spend just a few days there to try it out. There is a lot of trash in the water and the dive guides don't even try to clean it up - they say the critters enjoy living in it. The macro is great! Better than Anilao or anywhere else I've experienced. Every dive is like 80-90min, in shallow-ish (10-20m) water, no-very little current, treasure hunt looking for critters. No corals or big fish life.
Bangka is great all-around - decent macro, they said everything you can find in Lembeh you can also find in Bangka, but keep in mind the density of critters / speed of finding stuff is about half at best. In Lembeh the dive guides found one thing after another and there was no downtime / waiting around for them to find something. In Bangka on the macro dives there's definitely a fair bit of waiting around. I also didn't find the yellow/orange pygmies
they only had the normal pink ones and the black ones.
The corals at Bangka are the best I've seen anywhere- Sahaung which I've dived 5x (1x each day) even surpassed Sipadan which was my prior gold standard. And it's really really colourful soft corals - orange, red, green, yellows. The pinnacles at Bangka are filled with them - then add on top super dense / big fish schools and it's magical. Lots of giant frogfishes also. The water is much cleaner and clearer, from the dock to Bastianos you can see all the corals and fishes from the surface.
Luko is right, Bunaken is boring. The walls are ok - but not as good as Tubbataha imo. Corals seem healthy but it's all an ugly brown, very little color. Turtles are everywhere tho, can probably see 20 on each and every dive. I don't regret going because otherwise I will always wonder "what if", but I don't plan to go back. Next trip will be half Bangka and half Lembeh. Bunakan also had TONS more people and most of them very inexperienced, flailing around in the water types.
I stayed at Bastianos for all 3, transport in between took a good half day, they can only boat during daylight hours in Bangka and Bunaken, so you usually do 2 morning dives then do the transfer around 2pm after lunch, and arrive around 6pm in time for dinner. They seem to have suspended the direct boat transfers where you dive along the way. At Bangka and Lembeh there were days where I was the only guest, but Bunaken was super full (I don't know why).
I don't know if this issue is specific to Bastianos, but at all 3 resorts I found the food quantity to be lacking - and I am a 105lb girl. Taste was great at Lembeh and ok at the other 2 but not stellar. I usually have to ask for extra food and they will make you something - but most of the time they say they're out of whatever they served and you have to wait 10-20min for them to make something else from scratch (and I also felt kind of bad because it seemed like they're running low on food, I don't know if it means the staff eats less cuz I asked for more...) There is no a la carte menu to order from, or any choice. Wifi is also non-existent in the rooms for all 3 but decent in the restaurants. Hot water was great in Lembeh, ok in Bangka (have to wait ~5min but otherwise good pressure and heat), and horrible in Bunaken (very very little pressure, no heat - I had to shower in another room that's directly under the solar water heater for somewhat warm water and somewhat decent pressure). Also no bar, no spa in any of the 3 despite what was advertised. Bangka is the newest and nicest by far. Lembeh is the old Froggies and in need of renovation. Bunaken I think I just got unlucky with a room with no working shower - they did agree to waive the single supplement ($18 vs $110 room rate) to compensate which I don't think is enough but better than nothing.
If others have recommendations for other Lembeh and Bangka resorts with 1) good wifi in the rooms, 2) hot showers with good pressure, 3) a la carte menus / better food options, please let me know! I just signed up for Alex Mustard's macro workshop next year at Lembeh Resort so I'm hoping it would be better. Am thinking of adding on a few days at Bangka to dive Sahaung again but not sure if I want to stay Bastianos again.