I stepped up from a '82 Honda CM250C which had the same engine as the Rebel 250. That was the first year for the engine.
There is a big difference...... a good big difference
. Here in eastern PA, the 250 sometimes needed to be downshifted to make it up some hills and keep the 55 mph. A rider on the back and you really knew it and those hills where a challenge. The LS650 takes the same hills with ease and can easliy accelerate up them to boot.
With power come less MPG. My 250 use to get 75 mpg highway, My 650 gets 55..... on a good day, 45 on others. This MPG could be related to more bugs on the teeth (happy bike syndrome
) I do more zooming.
The 250 did 75 mph but that was about it. On my 650, I already went to pass and have been accel'ing
thru 80 mph when I realized how fast I was going.
The 650 is easier to work on, and the spare parts availability is the same since the LS650 is virtually unchanged where Honda has had several frame and body changes.
Hope this helps.
Edit: I notice school buses and Garbage truck more than semi's.
Edit -2 : 55 MPG with 2.8 gal tank = 154 on a good day, but you hit resv. at around 100 - 120.