I think you'll find it comes down to sailors rather than boats. In my view the Spitfire and F18s are well matched. I have done well on my Spitfire (within the club, racing against F18s) - I put it down to getting the crew right (far more important than the boat), working at making no mistakes and sailing no further than I have to. Check out the results on our club page if you want some club level comparisons!