Greetings

i had a Bionx 350 for over a year now and I am thinking to switch to Bionx 500. The main reason for wanting to do that is that I need a faster commute. I do about 21 km and it takes me about 45 min each way. There are a few hills on on this route, most of them fairly small and having the motor definitely helps. Without the motor I can do one way in about 1hr 10 min. I ride a Devinci Liverpool with Schwalbe Marathon Supreme. I switched from Marathon plus because ther were adding about 5 extra min / trip and the battery consumption was about 20~30 % higher.
I ride on a bike path, mostly shared with pedestrians.
Now, I hope to be able to cut down the time to 30-35 min but this means I am going to be racing like a maniac most of the time.

I was wondering what are your experiences with the 500 motor? Is the speed gain significant when comparing to the 350 motor?
Is it worth getting a 48v battery instead of the 37 one that I have? Can I burn the motor with tha 48v? Any advice would be highly appreciated.