Go bigger. I am looking to sell my ARC21 to get into a Tornado. The difference in bow bouancy and down wind spin performance is night and day. On the ARC21 I cannot PITCH if I try. On the H20 we still had to be very mindful. The extra foot and hull design is awesome for reaching and down wind performance.
Admit, I am not a top sailor but I have been on or observed most current designs. put some great sailors on the ARC21 and they will exceed the PN.