John
You really are asking the wrong people - they are great people - but they are a self selecting group.
After all what do you expect them to say - I test rode both, the Silverwing was best so I bought the BurgerKing? :roll:
So, you are not really going to get
the answers you want here BUT I do know there is a silverwing forum in the UK
http://www.silverwing.co.uk/forum/, (Edit - it is now defunct ISP problems and the forum owner now hs a TMAX!!)
For what it is worth - my take (and I own neither):
1. BurgerKing is heavier.
2. BurgerKing has arguably the better handling in the twisties
3. Burgerking has conventional brake controls (left back/right front).
4. Burgerking not available in North America with ABS (yet).
5. Burgerking has the bigger engine and probably the performance edge.
5. Silverwing has combination braking (left back+proportion of front, right front)
6. Silverwing (from 2002 I think) has ABS as standard.
7. They are both lardy arse machines - are you sure a 400 Burger does not suit your useage pattern?
Good luck in your quest.. please let us know how you proceed.