On the whole, the big ones are probably built to or near the quality of the Larry Smith (non-race) Scarabs. The smaller ones are more like the Wellcraft Scarabs.
I know I'm equivocating so I'm not sure if that's helpful.
If you are looking for an American boat around 21 feet that will withstand UK waters, you might be better off looking at Progression, Superboat Inc. or dare I say, Velocity.
I thought that having more patience was a result of my getting older. Turns out that I just don't give a sh*t.