Skiens,
Both brands are good. But there are better boats out there. Boice builds a bad ass boat. Wayne Adams of Sea people in Gold Beach Oregon builds a good boat.
With a 21 footer I would go with a small block V8, Like a Vortec 350. Stay away from he sportjet, They dont get the fuel economy that a V8 will give you.
Jetcraft and North rivers quality has went waydown since they started mass producing boats.