Well, it kinda depends on your budget & which area you are focusing your diving on..
By the way, I just came back from Sipadan heh... and i stayed at a few places so maybe i can give you a better idea of what you should expect...
hopefully you'll benefit from my experience..
First of all, we dived at 3 separate locations- the Mataking/ Boheyan area (further up north, close to border of phillippines in the celebes sea), the Sipadan/ Mabul/ Kapalai area, & lastly the Roach Reef area... we stayed at different locations for each area dived..
When we dived at Mataking & Boheyan, we stayed on Semporna mainland at Dragon Inn. It takes about 45 min boat ride to the dive sites. Dragon Inn itself is not too bad, its built on stilts over the water (which is so polluted that i doubt any fish can survive in it, but no smell though), but more importantly the rooms were clean & big, & fresh water supply all day long.. i had a TV tho' i'm not sure if all the rooms have..so i would rate it a 'value for money'.
Breakfast is provided but be warned it consists of only a cup of tea/coffee & 2 slices of bread. picnic lunches are usually provided by the dive operator which you take onboard with you the boat. Dinner is NOT provided so you have to forage around yourself but there are plenty of restaurants around. Diving there is not as fantastic as i was hoping tho.
After that we moved to the SeaVentures Oil Rig platform to dive sipadan, mabul & kapalai. Honestly, tho they welcome you with a glass of orange juice when you arrive, & they provide you with 4 yummy meals a day as well as free flow coffee/tea/milo... as well as clean towels daily, the rooms were small, windowless, with a funny smell, & i suspect the blankets have serious bed bugs infections..
not recommended for the claustrophobic or cleanliness freak. So think twice about staying here, but then most of your time will be spent diving & the only time you'll b in the room is when you're sleeping.
Also, tho they promise you unlimited reef dives, the current there is so strong that they dun even recommend u dive under the platform itself.
by the way, the fresh water supply on the oil rig is desalinated seawater, but the degree of desalination is questionable. ie you'll still b bathing & brushing your teeth in relatively salty water..
the only good thing about the platform is its proximity to the dive sites, & the relatively cheaper price compared to the resorts on the islands.
the last area we dived was roach reef (a privately owned man-made reef) which was interesting. same price as oil rig but you get resort service, unfortunately it's almost 45min from Sipadan, & another 45min to the mainland. But i don't think you'll be interested in diving this area so i won't go into too much detail abt this part of my trip.
My Recommendations (you can disagree heh)
1. Length of stay- if u will be there only a few days, i suggest you concentrate on diving the sipadan/mabul/kapalai sites. there's a reason y they're one of the best dives in asia. if you're staying longer then you can consider a Dive Safari.
2. If you're diving the S/M/K only, then stay on the islands...
if resorts are way out of your budget, go with Scuba Junkies, they offer backpackers acommodation on Mabul.
If you decide to stay on mainland Semporna, go with North Borneo Dive & Sea Sport, they are one of the largest dive center there, with 4 speedboats & located right in Dragon Inn so it's convenient.
3. Price Range- the prices are very competitive, & it's not necessarily cheaper to walk-in & book a dive only when you arrive there. Also there's the Sipadan permits to consider. Book at least a month ahead. Pls note that you can only dive Sipadan on ALTERNATE DAYS. This is a friendly agreement between the dive operators.
4. Peak periods are during April-Aug so expect higher prices, I went in April & paid US$900 (all inclusive) for 8D/7N with 22 dives. This is not an endorsement of my dive package but a rough guide for you.
There hope these info will help! More importantly, have loads of fun there!
Cheers!
Violet