Well - having surfed for many years, I must have used pretty much every fin system going. Over here in the UK FCS have marketed their product well and have the market sewn up.
It's a bit self-fulfilling - the more popular they are, the more shops stock them, so the more readily available they are so more people choose to use them as they are easier to get hold of, so the market grows, so more shop sell them etc etc etc.
HOWEVER - I don't personally think they produce the best system though. My favourite is Red-X to be honest.
Thoughts anyone???