Top pipe makers will single out "good" briar blocks, i.e. good grain etc. They probably will expend more handmade effort on those burls, since they could yield a better "finish" and thus a higher price. So if it looks good, it "PROBABLY" had the extra attention of the pipe maker, and it "MAY" thus be made a little better than its ugly-looking cousin. And priced accordingly.
Then again, you could have a butt-ugly pipe that can stop a clock, yet smoke like a dream. Or a picture perfect finish, and a lousy smoker. Each pipe is unique, and like books, can never be judged by the cover.