Wouter:
The Prindle 18 is a tough boat to sail at 280lbs (suggested crew weight). It doesn't tack well (especially above the 280 crew weight). The long waterline and low prismatic value make the boat a beast to manuever especially intacks in choppy water. The Prindle 18-2 sits up much higher and has a nice centerboard to rotate around. The buoyant hulls and high prismatic value on the 18-2 mean the boat will have a lighter helm and be more responsive especially at higher crew weight values.
I have personally beaten the Prindle 19s boat for boat in winds over 20 knots on a regular basis with the Prindle 18-2.
I hope this answers your question!
MM