Which light is better depends on the PAR (or possibly more usefully, its PPFD, which most reputable grow light companies provide an image of the PPFD map) and the spectrum. If the PAR and spectrum are right for what you’re trying to grow, any light should work. The only other things to really consider from a usability perspective are the IP rating (how dust and water resistant/proof the light fixtures are - low ratings may eventually be damaged by high humidity, so obviously not ideal over big tanks), how long the light will last (assuming the light is of decent quality manufacturing, see the link below), and, in some cases, the heat put out by the light.
Of course, the wattage is important, and the aesthetics of the light may be important too (depending on the application), but these aren’t truly important to the actual function of the light. The wattage is, however, important for your energy bill.
With regards to watts and the function of the light: watts not always useful for determining if a light is good or how powerful it is - for example, I know of one LED company that markets two lights with the exact same specs, but one is 600 watts and the other is 1000 watts; they admit that there is literally no other difference between the two lights (they have the same PAR, spectrum, features, and everything), so going with the "more powerful" 1000 W literally just raises your electric bill with no benefits over the 600 W).
Edit: forgot to add the link-
Long post but, here we go. I'll start at the basics. In layman's terms, essentially when a LED is created, there's a substrate that is laid down, usually a crystal lattice. This substrate sits between your LED and your wafer from the chip. This substrate sits on top of that wafer and...
www.reef2reef.com
