It depends on the specific corals you'd like to keep. Personally, I wouldn't recommend PCs for a 90g. When we had PCs on our 90g, mushrooms only survived near the bottom of the tank (on top of a 5" sand bed) -- they didn't thrive. Since switching to T5 HO, they have better growth and color. There's also several hard corals doing very well near the top of our tank under the five 54w T5 HO bulbs we're running (2 actinics on a normal T5 HO ballast; 1 actinic, 1 10000K, 1 12000K overdriven on an IceCap 660 ballast -- each with their own IceCap SLR reflector). We have several Acropora, some Montipora, a couple Stylophora, a Pocillopora, and two different Seriatopora and they've all been growing and maintained good color.
If you don't want MHs, T5 HO is a good alternative, as long as a suitable T5 HO set-up is chosen or DIY-ed to fit your needs.