The problem with using any type of flourescent bulb as the primary light source for high light demanding corals is the fact that they just don't have the water penetrating power that MH does. Total light output may be comparible to a similar wattage MH setup, but because of the fact that the light generated by flourescents is spread out over a long tube instead of concentrated into a very small area like the MH bulb does, you simply don't get the same water penetrating power.
I have read several posts from people that keep SPS under non-MH setups, but I think there are a lot of varibles that need to be looked at....ie. species of SPS coral, placement in the tank, amount of flourescent light provided, ect...
On the PC's...watt for watt they have the best water penetrating power of any flourescent on the market currently. However, there has always been some debate as to the quality of spectrum produced by these bulbs. As for heat....I have a VHO/PC combo above my reef, and I can testify first-hand that my 55W PC's produce a considerably larger amount of heat than my 110W VHO's.
Sure. you can keep higher light demanding organisims under an adequately intense flourescent setup...I have a large t. derasa clam that has been doing quite nicely under mine for many years now...but if your goal is to keep SPS and you don't want to be restricted by light at all, your best bet is still MH's....
MikeS