Hello,
I sould be tempted by the 6500, as the location of the connections would permit to fot the opening side of the filter on the timing side of the bike (the other one has both connections in one direction, and to fit it cleanly without too many tubing, you get the opening side facing the chain...)
I'll buy it too, my engine has been just remade, and I intend it to last a long time !
cheers Claude