Be sure you get HO lighting. A lot of seller seem to forget to mention that the fixtures and bulbs are NO.
I agree with Pampee. Bulbs for t-6 will be hard to find, maybe expensive and nowhere near the flavors available to the T-5 user.
All that being said, some people like yellowish 6500 K MH bulbs and rave about the growth so its all about what you like and making an informed choice.