Four Winns, Larson, Glastron, Marquis, Champion, and Wellcraft are all the same company.
Four Winns is a superior boat to Larson and Glastron. (Larson and Glastron are actually made in the same factory).
Be careful with that first statement.
All of those brands (and more) are in fact all owned by Genmar. However, most of the companies operate independently of each other. The only significant exception is the Larson and Glastron VEC boats as you mentioned.
Four Winns boats are all unique designs that are not shared with any of the other companies. Four Winns and a couple others have been owned by Genmar only since 2001. Four Winns was owned by OMC before that.
So for the original poster who is looking at model year 2000 boats the entire Genmar thing doesn't really enter into the equation.