Help-Fanatic Mega Cat or Mistral One Design?

Can anyone tell which board better to choose for raceboarding at lakes? I don't know, which is better. Someone offers me an old Mega Cat (one of the first models, may be year 1990-1995 or so), the other offer is used Mistral One Design (produced approximately in year 2004, it has long red line on the right side). I have read that Mega Cat goes better upwind because of a longer daggerboard, but it's 250 litres and 380 cm long. One Design is 235 litres and 372 cm long, but it's about 2 kg heavier. Some surfers write that Mistral OD does not sail good in light wind - is it true? Which of them both is faster in strong wind? Which is more durable?