Hi Ownplanet,
If you want the best lights to grow you need to look for broad spectrum lights. This means the entire spectrum, not just blue and red (Burple) spectrums. But also the white/green in the middle. Most LED Grow lights don't have white (which really is a blue light to the plants, but looks white to humans). The way many manufacturers work it is like this, blue spectrum is on the left side of the spectrograph (420nm) red spectrum is on the right side of the spectrograph (720nm). This means the graph has 2 peaks, one at 420nm and another at 720nm, they call this "full spectrum" because it goes from one extreme to the other extreme, but those are completely dead in the middle between the blue and red. This is total BS! Lights will hugely benefit from more than just blue and red, they need green. Proven by a plant scientist named Bruce Bugsby. One of the smart guys who worked on the early sustaining life space program.
The other issue is the wattage claims. Mars Hydro is one of the bad ones, they claim 400W, but in reality it really is only using 162W. And this 162W is putting out a very poor grow light spectrum (Burple). With low par (Umol) values.
There are only a few broad or full spectrum lights out there, ones that have green LED's in them. There are even fewer that publish real and honest performance numbers. Even fewer that don't exaggerate the results!
LED lights are often compared to the HPS wattage equivalents, this is totally bogus. It is not about wattage, it's about micromoles (Umol). Umol is the photosynthetic spectrum of light, Humans cannot see this. But plants can and use it for photosynthesis. The other issue about using watts and HPS comparisons is that HPS lamps waste up to and more than 60% of the wattage in heat output.
Quality LED's grow lights also don't use cooling fans.
To the OP: it's not at all about lumens. Lumens are for Humans! It's what we can see and perceive as light brightness. Plant growth is about Umol. Typically plants need a minimum of 180 Umol to be happy and a maximum of around 800 Umol. Above that there is a risk of burning the plants (sunburn). It's also about DLI (Daily light integral) this is how many umol's plants receive during a photo period. With weed in flower it would mean in a 12 hour period. Most plants are happy between 5DLI and 35DLI with pot being on the higher end. Typically with pot a DLI of 18-25 is about right. If you get above that the plants start spending more energy trying to shed the extra light they receive than they spend in photosynthesis, very counterproductive. Our sun emits as much as 60 DLI at high elevation bright sky. This is why often times the plants do much better in the shade or partial shade. Some of these super high output grow lights, LED's and HPS put out an astonishing 95+DLI.
Ask if you'd like to know more details.
Happy Growing,
TTKlaus