5w are sketchy to me, but I don't research all of them too gnarly so. 3watt chips are the most efficient from what I can tell but not too many companies are using the 3w to their fullest yet IMO. I think of 3w vs 5w the same way I think of (2)600hps vs (1)1000hps.
Currently Apache is using 1w driven @100% and they have more output than most every 3w and 5w using units still. I think eventually they will more up to a 3watt like chip but I doubt 5w or higher till technology seriously changes.
Some say driving LED's at full power is bad and limits the life of the bulbs, the higher the wattage this seems to be somewhat true. But I am not 100% sold that they shouldn't be driven @100% if they could be technically speaking. 50,000hrs is ten years of 12/12 so even half that would suffice if it performed like a champ. In the end I really only care about "what is the par output of the unit." If a 5w has the higher umole output, I would go with it I just haven't seen any yet. I have seen 80w chips now so who knows what will end up being the best. But for now it is still new territory.
Here is how I look at LED's in order of importance.
1) What is the par output in umol's (most companies don't give one on their website and that just pisses me off)...minimum 700umols@12" is the lowest end of my attention radar. 1000hps's puts out 1800umol@24" so that is my real goal. Yellow(lumens) light that is not all absorbed(wasted) is still in the par spectum, so 1800umols LED PAR(wavelength specific) output would be more to the plants than 1800umols PAR(the whole mess) from hps.
2) Wattage to achieve output. (first total unit draw, then diode wattage and brand)
3) Coverage size and umol dispersion over the area (only strong in center or is it spread out)
4) Spectrum/wavelengths
5) Price
6) BS advertising/company image/knock offs on the market. (maybe they are the knock offs?)
Just the ways I personally judge all of them.
