Aloha Dee,
It has been said many times before on SB, bad op's do not survive on Maui. The Four Seasons Wailea is one of the premier properties on Maui, continually listed in everybodies best of the best lists for Maui, the state of Hawaii, the USA and the World. A bad dive op would not be allowed to do business there. An inexpensive one would not be allowed either.
If price is how you will make your decision, call them and ask them how much it will be. Take into consideration that their price is all it will cost you, there will be no transportation costs. They also may be more flexible with the when's and where's, as well as last minute changes; guests call the shots at top of the line luxury resorts. If you also want to do some recreational dives, ask for a package deal.
Then call the Kihei dive shops and ask them thier prices, as well as where and when the dives will be (boats are usually very early). Do you have the use of a car? If not there may be some walking or taxi rides involved. If you value your time as much as your money, the convenience of diving on property might make it an exceptional value.
Remember, Hawaii Ohana SB'ers are not all authorities on Hawaii, or Maui. Only one previous poster answers any part of your origional question and that one calls Maui Undersea Adventures very professional. Eduardo also has a similar number of posts in the Ohana to his dives in Hawaii, which I find very refreshing.
As with the other posters above, mine is just advice and opinion. The difference is full time residency and years of full time guiding here. What ever you decide, I hope you come visit me and let me know how it's going. I'm with Ultra Dive at the Wailea Renessaince, less than a mile down the sidewalk just past Ulua Beach.
Aloha,
Steve
PS to Kris; if you've already seen numerous open water check out divers freak out in 2' of water, are you sure your diving with the right people? Properly prepared students almost never freak out in 2' of water, or the calm crystal clear waters of inner Molokini.