one big dif the nuvi did away with the big buttons on the side of unit and went tottaly touch screen i like being able to zoom when wereing heavy gloves not posible with touchscreen however i suspect that the nuvi will have more detail on poi"s not sure though im not that familiar with the nuvi
i got the zummo 450 for under 500( if u dont need bluetooth to tell u directions) the discontinued 450 should be even cheeper. u can still hear the 450 if u plugg into aux jack and load mps on sd card to hear tunes while on aux. i find just glancin i dont need the bitch tellin me every 2 minutes and if i miss a turn it will reroute real fast.
Zumo is water and shock resistant and more motorcycle user freindly. Any time I buy electronics I check cnet.com. You can get good reviews and a list of sellers and their prices. You can find the Zumo 550 for at least $100 less.