What is the difference between a Thule and Sport Rack roof cargo box?

I'm trying to figure out whether the Sportrack make is as good as the Thule make. There seems to be a large difference in price.|||They're just different brands.|||I'm not certain on all of the specifics, but Thule has been around for years, make great products and is usually the first brand I think of when someone says aftermarket car accessory... bike racks, ski racks, luggage, etc. I personally don't need or use one as I out everything under the tonneau cover on my pickup truck, but I hope that this helps some.