I just stayed at SMART and then switched for three nights to Mabul Water Bungalows and agree with DontLietoME. SMART is a very friendly and efficient place with great diving and views and relatively nice bungalows. The problem is that there is no decent cable TV and so it is difficult to follow news or sports if you are on a long stay as we were. Also, the one mark against SMART is the food which is just adequate. The food at the Water Bungalows was outstanding (shrimp or lobster almost every day, but with other options always available), the rooms were tastefully decorated with cable TV, their own porch looking over the water and a "real" bathroom, and the diving is very convenient to the rooms. It is a relatively small place, only 12 bungalows in use, with personalized attention. Equipment rental, office and internet are at the main resort (SMART), a short bike ride away on supplied bikes. I met the owner, Robert (Chinese-Malay), whom I liked very much. He says he does not plan to expand the water bungalows other than to finish the bar area (which is not really up and running, but they will make you a drink and cold beer and wine are always available from the kitchen area) and to add a spa. I liked the fact that about half of the employees in the overall operation are Mabul island residents.
The routine for diving is two morning dives at Sipadan, divided by about one hour on a small section of beach that can still be accessed by the boats. The rest of the island is off limits for sea turtle conservation purposes, among others. In the afternoon, the dives are all around Mabul Island or at Kapalai. The viz in early Jan on Mabul was very low, but there were interesting things to see (lots of crocodile fish, a beautiful bright orange frog fish, a giant moray, some pretty ribbon eels and nudibranchs). The viz at Kapalai was a bit better and much better at Sipadan, though not as good, I am told, as in April. Apparently, December - Jan is rainy season in Borneo, which suprised me because that is the dry season in Thailand. April is the period of flattest and clearest water.
We didnt see the big school of chevron barracuda and were told that they now come and go and may be disturbed by all the diving. We also did not see the bumphead barracuda that I saw frequently when I stayed on Sipadan six years ago. But we did see a hammerhead shark, a very large gray shark, a multitude of white and black tipped reef sharks, a leopard shark, several large sea turtles on every dive, and a large school of jacks.
SWV is, I think Japanese owned and largely patronized by Japanese. I never went there, but that is what I heard from a dive master at SMART. It seems to be the same sort of physical arrangement, but perhaps larger, than Mabul Water Bungalows.