T5's or HPS/MH lights?

You can be successful at both! It just matters on your style of growing. I would prefer the HPS/MH system over the T5 system. But which ever you pick, I wish you the best of luck with it!

 

Between T5's and a 400 hps, it is a toss up. More penetration with a 400 of course, but I keep a flat canopy with little underneath regardless and T5's will yield similarly per watt, albeit smaller buds. If you move up to a 600w hps you'll be able to get fat dense colas the T5 just can't compete with. Some strains seem to perform better, in visual terms if not potency, producing frostier bud than under the hps, but it's always fairly small. I've only used the 4 bulb two foot T5's, though, so maybe the bigger 4 foot 8 bulb 400w (approximately) will perform better. I plan on getting one.

 

I have multiple 96 watters (2 foot four bulb) and they all came with reflectors. I wouldn't bother getting any without. The footprint is not much more than a few inches beyond the perimeter of the refelctor, in terms of effective flowering, and you can and should keep that flowering canopy literally millimeters from the bulbs if you can monitor it well. In veg, you can get away with up to a foot of distance and double the footprint and still get a large healthy plant eventually, but a 600w MH is going to have much more penetrating power and a wider footprint than 600w of T5's.

 

Compared to a 600w or a 1k hps, the T5's will yield, watt per watt, less and the buds will be much smaller and airier. However, they do fine in flower, if you keep that canopy close. I noticed no difference with multiple clones tested for multiple strains in terms of flowering time under HPS or T5, you just don't get the same kinda bud. That model you linked to is essentially what I have. Number of plants is entirely determined by how large you let them get in veg. One will suffice, as the footprint of those lights is a 1 by 2 foot rectangle. Veg a few plants and use LST to shape them to conform to that footprint precisely. I typically get 2 ounces out of one of those fixtures, so about .5 grams per watt and it's always very good bud. One of my strains gives me large thick buds under the 600w hps but the small frostier bud I get when I put it under a T5 is just a better smoke/vape. It's all a matter of experimenting and finding what suits your taste. If commerce is the goal, always go with HPS for flowering, since you're most likely to get a large dense bag appeal and a good amount of lower bud to fatten up the yield. T5's are worth a try, regardless. They are complete grow lights, for the personal grower.

 

Another thing to consider with a small T5 like that is that you can grow on a shelf in a closet with no heat issues. The distance from the canopy to the light can and must be verrrry short to get good bud. I've grown in a 2 by 1 box only 23 inches high with a heavily trained plant in a flat rectangular makeshift soil container with great results.