Rob I agree with what your saying but wasnt the valver you owned a poor one, or am I thinking of someone else?
I think if you get a valver that it a good and fast one and a not so good willy that isnt really up to scratch then there is not loads of difference. I think the main things you notice with the willys is the low down torque, they pull so well from anywhere in the rev range, so in the speeds higher up the gears they are a lot faster. Where as the 0-60 of the 2 is very similar if not hundreds of a second in it.
Ive had a few comparrison tests with different kinds of willys, 1s, 2s and 3s, in all different kinds of conditions, from fairly standard to highly tuned. In my personal opinion Id say a good valver vs a good willy then the difference is noticiable but not like from a valver to say a completely different car because in essence they are the same car, the williams was based on the valver!
However, I think to own a williams is more of a status as aaronc saids they were limited and so become even more appreciated!
If I were you I would possibly move onto another car, experience that for a while and maybe go back to the williams after, as I know its a car one day I want to own, just to see the major differences for myself and say Ive owned one!
Danny