Pendants vs. complete fixtures is completely up to you.
Do you have a canopy already? If not, then maybe complete would be the way to go. If so, maybe pendants and retrofit kits would work best.
Personally, I'm not sure 250w MH's are going to reach the bottom very well of your tank. It may not be an issue, depending on what corals you want where, but 400w may do a lot better for things on the sandbed (assuming your 220 is the standard 30" deep).
At the same time, I'm not a lighting guru.

I am, however, a T5HO fan, but they also don't do real well down to 30" I don't think. I can say that mine do great at 24", though. I have a crocea who has been very happy on my sandbed with T5s. If I put it any higher up, it bleaches out!
Hope this helps at least some.
Brandon