Here are my thoughts...
One 10 watt chip produces more light for the watt.
That said no one who has used the Iwasaki 6.5K to grow talks about how well it makes their corals look.
3W LEDs??? They differ hugely in quality and brightness. Counterfeits to unbinned to binned Cree X series...Either way a huge variance in looks if you choose wrong.
HeatsinkUSA has a T-Slot Heatsink you can easily fit any custom acrylic housing to.
It also gives you much better thermal management so you can choose the better Cree or Luxion LEDs and keep them cooler than their design specs.
This will give you a brighter more longer lasting light.
You more often than not get what you pay for but you can choose the better parts which will cost you less in the long run.
Also never judge a LED Fixture by watts...Like judging a motor by cylinders...
Cheers
Bill