While there are some decent LED downfiring bay lights the cruel reality is that right now about 95% of them are less efficient than fluorescent baylights and cost a lot more. Pretty sad when LED retrofit bulbs are beating LED based shoplights in terms of price / efficiency ratios because you have a wallet and some lighting maker pays their marketing dept more than their engineers.
To add to what Purduephotog said, I've seen 4x48" shoplights on sale at said Home Depot for less than $50 with electronic ballasts and bulbs. That's ~8,000 or more lumens at ~70 lumens per watt legit for less than $100. I'm not sold on T5 *unless* you have a need for high power densities or are willing to spend extra money on a hyper efficient T5 reflector to get the most photons from them.