IF YOU HAVE THE CHOICE, DO NOT GO POWER COMPACT OVER T5.
Never skimp on lights or filtration. You will end up rebuying these items later!

Power compacts start to lose their effectiveness at 3 months, where as T5 is 18 months. Power compacts are hot, and use more electricity as well. T5s are used on alot of reef tanks overseas, some tanks are purely T5 driven. You really won't find that with power compacts.

THE BEST setups you can buy for T5 are the ones with individual reflectors. Tek or Icecap Reflectors are the best in the biz. Icecap makes the best ballasts for T5s as well. A retrofit kit is the way to go if you have a canopy, since if a part breaks, it is easily fixed. An all in one fixture could have a failure that leaves the entire set of bulbs dead, and fixing that is much more intensive.

My tank is a 75 which is 48" and I use a combo of 6 T5s and 2x250w DE Metal Halides