No comparison, I have a 4-5 mile long hill close to Monticello, NY, highway 17W, the 300 will hold 75 in 6th up that hill and roll on throttle and it accellerates! Slowly but it goes faster. That was one up with a +1 CS sprocket too.
The 250 would do it at 70-75 with downshifts mandatory. Don't downshift, you drop speed like a stone.
I rode the 250 locally 2 up, forget about it. It will pull it but it just bogs untill you get above 7k. Again, I can ride 2 up and never exceed 7-8k and move faster than I need to. I just don't have to stretch the throttle cable like the 250.
Some cars struggle up it on the shoulder at 40 MPH, my old Dodge Caravan towing a tiny aluminum boat was one of them.
2 up the 250 can do it, but it lags and you feel the weight alot via throttle inputs. With taller gearing, the 300 really isn't even affected. I was chatting with my dealer yesterday and he was still surprised by the pull from the bottom just riding mine around the parking lot. The 300 moved the bike from what the 250 version is to a useable moto in every way powerwise. When you ride the 250 you accept certain things, not so on the 300.