T5s are amazing. The secret to the success of T5s is in the reflector. You need to get a fixture with a quality reflector that wraps around each bulb in a "gull wing" bent pattern. This allows each bulb to be individually reflected. There's a lot of cheap T5 fixtures on the market that have inappropriate reflectors. Make sure to research and get the right one.
T5HO with proper reflectors are every bit as good as 250W MH lighting. In fact, down to about 22", the T5s put out more PAR.
T6 are NOT HO, they're normal output, not good at all. PCs are okay, depending on what you want to keep in your tank.
I have a 75 with a 6 bulb Tek5, T5ho, fixture. I keep mainly SPS and clams. Everything's growing like crazy.