It all depends on what you really want to do. Your best bet is to use different operators if you want to see different things.
For shore diving I would recommend using Maui Dreams in Kihei. They've got a great staff who are willing to talk shop and local conditions, and they are located in a good place to hit the good dive sites on the south end. Makena, Ulua Beach, and Ahihi Cove are all only about 10-15 minutes drive from their shop and these sites are consistently good quality shore dives, especially for people who need a calmer/more protected place to dive until they get back in their comfort zone. If you're staying in Lahaina there are a bunch of cookie-cutter operators who will rent tanks and I've found them all to be fine.
For diving Molokini I recommend Ed Robinson or Makena Coast Charters. I've always had a good time with the crew on Ed Robinson, but they are a fairly mechanical operation: they tend to dive the same handful of places over and over again. The captain for Makena Coast, Steve, is much more flexible and is willing to do some great dives when weather permits. Also, his crew is a great bunch and the service on the boat is above average. Maui Dreams also has a great schedule of dives, and they do some boat dives that the other operators don't, like the Carthiginian.
For Lanai just about every operator does the same dive, so you really can't go wrong. Again, check with the three places I listed above and see what their shedules are like. And don't worry too much about the price because all the operators are going to be in pretty much the same ballpark.
