Heya was just thinking about this and wanted to add my 2 cents.
The Ray II is 39 watts and 40,000 hours in 4ft configuration. ~$170
A comparable high end 2 bulb t5ho is 108 watts and high end bulbs are rated to run around 20,000 hours. ~$100
It costs about $8-10 more per year in electricity to run a T5ho based on a quick generalized number crunch.
So ultimately you'd save ~$10 and have to change bulbs out twice as often per the ratings. The big difference is you can change bulbs out on a t5ho a lot easier than you can on an LED fixture. I spend <$10 shipped per 4ft bulb for ge starcoat 6500k and they do a great job at growing plants.
LEDs are cool, and the sleek design is nice to look at, but I don't think that the savings is a selling point for me until the fixture prices come down more. As it stands it really doesn't save all that much and I don't think I'd be up to changing out burnt LED bulbs. Not to mention the comparable t5ho fixtures are nearly half the price.
Definitely not trying to convince you either way, it was just something I was dwelling on when planning a multi tank setup.
On a side note,
fish need it;lights; food;Sponge has a 50% clearance on everything, and their 2 bulb t5ho fixtures are 89.99. So it'd end up being about $60 shipped for one of their fixtures right now.