What lights for a 2'x3'x6' tent?

IMO - Neither is perfect. I'd go with 2 xs1500 in this case or look for altenative with higher efficacy. This assumes you plant to grow photoperiod plants. If exclusively autoflowers, the smaller 95w lights might be better. - 2 xs1500 gives you more options for use despite being slgihtly overpowered. can cover a larger area if needed. You can likely find 10-15% off coupon for this light. That would make it same or less than the HLG. heatsink looks equal or better, too. - 2 hlg rspec 100 would be slightly less powerful but still damn near "max" DLI over 12 hours. If you plant to exclusively run autoflowers, this might be the better option.. - Alternatively -- any light or combination of lights that provide 500umol/s will do a good job for photoperiods and anything around 333 will do well for autoflowers in a 6 sq ft area. If you find these specs with better efficacy (umol/J), it will save you money on monthly bill and likely last longer due to less heat produced while providing same amount of light. The other thing to focus on -- build quality, like heat sink... as well as distribution of light. the more it is spread out over 6 sq ft the better. a light frame that is a few bars is better than a quantum board in this regard. Why (math)? convert area to m^2: 6sq ft = .5574 m^2 (you really don't need that many digits) Then, let's work backward from 12/12 flower cycle, because it requires more power per hour. 35-40 DLI is roughly 900 PPFD over 12 hours. 900ppfd * .5574 m^2 = about 500 umol/s Roughly the most you can give to 6 sq ft and not cause problems given ambient co2 over 12 hours of operation. You may even need to dim it 5-10%. This is also a benefit, as your diodes inevitably dim over time you can continue to give the same DLI with a little bump to power as it slowly loses efficacy over 50,000 hours or more.. So, any light or combination of light that provides roughly 500umol/s is a good option for photoperiod context. If doing autoflowers you only need 2/3rds of that or 333 umol/s over 18 hours to give same "38.9 DLI" as the 500umol/s over 12 hours. If you want to run different hours of use, like 20, it is proporitonal as you can see here. 12 -> 20h is 3/5ths of power over 12 hours needed as opposted to 2/3rds. DLI is the key. similar yields will result at similar DLI, all other factors the same This estimate is for upper level of light applied limited by ambient CO2. With tightly controlled VPD and 1300ppm co2, you can probably give 125-133% of each suggestion. 35-40 DLI is what you want to work backward from using area of coverage to determine how many umol/s you want in that area. you probably cannot tell the difference in results with your eye between a plant with 35 dli and a clone of itself with 38 DLI. It's a grey area that we shoot for and then trial and error to dial in to what results from local environmental variables. Being a little over or under is no big deal. Being a bit over is the better way to go. XS 1500 gives about 340-350 umol/s x2 = 700umol/s .. so you'd be runing these at 70-72%. This is actually a better wattage for thise number of diodes. you'll get improved efficacy (less any loss from running driver lower) and longer leaf with less heat produced. HLG rspec 100 gives about 220-230 umol/s x2 = 450 umol/s. 10% short so 38.9 x.9 = 35 DLI .. these will run at 100% and probably create more heat than 2 xs1500 running at 70%. diodes will die faster. Neither of these will hit 50,000 hours and still be 90% of intensity given how hot the run the diodes. they both have less life than advertised due to how hot the run the diodes. anything > 0.25w/diode is going to be a reduced longevity from "50k hours." Since the xs1500 would be runing at 70% --> .7*150 = 105w. So 105watts / 288 diodes = .365 watts per diode. the hlg is worse when comparing what would be used in your 6 sq ft. anything over .4/watt starts to really go downhill efficacy wise = more heat, less life, more watts to produce same amount of light.