Actually, I wanted to buy a Zumo210 or a TT U.R. (about 300 euros). But since there is also a mobile phone purchase (Motorola Defy) the question arises whether the motorcycle navi is not superfluous? The Defy is waterproof and offers Google Maps navigation in the flat rate. However, I do not know the disadvantages of smartphone navigation with motorcycle. Who uses smartphone navigation on the bike and can give me tips?