[rks]

I would be less concerned about a 150's hill climbing ability, and more concerned about a steady diet of highway speeds. I have no problem with the 10%+ grades I encounter every time I take the scooter out.......but I don't run highway speeds ever. My scooter rarely sees 6000 rpm's....most of the time it's somewhere between 5400 and 5700, and at this rpm, will pull a 10% grade without a drop in speed, and without using full throttle.

If by "flat and highway speed" you meant you need to be doing 55 - 60 mph.....you better pick the 250. They are much better suited to running an open road.