I have used both, and both were excellent. Mark Tinsky's briar was a slightly bit larger, but that may just be the batch from which it came. Both were of excellent quality and the price almost identical. I can add, that my self-carved pipe is the best smoker I have. Better even than my Preben Holm Ben Wade.
Both Pimo and Mark Tinsky are excellent people to do business with, and you can't go wrong with either. They are stand-up outfits.