animus_divinus
I agree with frnz571. Neither one, the T5 fixture (even with two
bulbs), or a single 100 watt
hps will produce much of anything in the way of fruit. Either way you'll wind up with spindly plants with little to no fruit. The fruit that does develop will be way under size (and may not even taste good). Keep in mind that just comparing lumens bulb for bulb (HPS to florescent) is like comparing lamp oil to jet fuel (not comparable). It's not what the bulb can put out at the glass/bulb surface, it's what the leaves receive that's usable to the plant. Even though florescent
lights can be placed closer to the plant because of less heat buildup, that still dosen't offset the usable light "drop off" the plants actually wind up getting from the light source (even trying to reflect it). I'm not sure what variety's of tomato's your planing to grow, but if they aren't expected to be larger than 3-4 feet they must be bush variety. Even so, 1-100 watt HPS bulb again won't be adequate if you want it to produce well. Bottom line your better going with HPS, and ventilating if necessary. For more even coverage of light you can use multiple 100 watt HPS bulbs, instead of one 300-400 watt bulb.
P.S.
Thanks frnz571, that's a great example of the light drop off. Even if the florescent bulb was touching one side off the plant (at the bulb surface), the leaves less than 1-1/2 feet away (18 inches) are receiving about 1/3 the usable light. That dosen't even take into account light shading from the plant foliage.