I like the clown better.....I'm sure you know this but I'll let you know just in case...Both these are kind of hard to keep, kind of an expert only fish. I don't know how much experience you have, I don't mean to offend..
i've never had a clown tang but my powder blue had ick for what seemed like all the time...entire tank got it finally lost 8 or 9 fish....won't have on again....maybe it was me but something to think about
PB
I had one for 4-5 years when I had my first tank, with no major problems. Have tried twice to keep clowns with no luck,(guess that means I wasn't suppose to have one) so go with the PB.
I had a clown quite a while ago and he jumped ship. I've had my PB now for about 3 months, no ick, no nothin. But I also run ozone and feed well and keep water perfect.