my advice to you is do as i did and read as many reviews as you can on both models. some reckon that if you are going to do a lot of two up touring then go for the 650. i,m on my second 400 burgman. i chose it over the 650 for three main reasons. one the massive price difference, two, the weight difference, the 650 weighs more than the hayabusa and thats one heavy bike; three the running costs both in terms of mpg,and servicing. overall the 400 still remains the favorite but ultimately the choice is yours. both scooters are excellent machines.