I never had either one but I know my Tangs! Anyway, I think you meant this one, and not the Thompson's one?
http://www.liveaquaria.com/product/prod_display.cfm?pcatid=334&N=0
My buddy has one of these in his tank along with a Naso, Hippo and Sailfin and they all get along fine. This one doesn't get as large and eats its seaweed like any typical Tang.
The powder brown can be confusing. There is the Acanthurus japonicus and the A. nigricans. They are often confused with each other as people call both of them "Powder Browns." They do look a lot alike.
The Acanthurus japonicus is definitely the hardier of the two whereas the A. nigrican does not do well in captivity in comparison. So if you choose one of these I would make sure it's the Anthurus japonicus.
I'll try to put a couple of pictures up for you to see their striking resemblance (can't find it now for some reason).
This one also doesn't get as large as some other Tangs.
Heading off to look for that picture...
Edit- found a picture of both of them next to each other:
http://www.saltwaterfish.com/vb/showthread.php?t=263780
It's about halfway down while scrolling. They're both beautiful fish. I'd love to have one.
I keep editing! Anyway, here's an excellent link to further explain the difference of the "powder browns..."
http://www.wetwebmedia.com/GoldRimSs.htm