Email: iPad wins
The iPad's Mail app provides a clean client for your email work, keeping controls front and center and providing nice usability touches such as options for message threading and per-account signatures. The all-inbox view makes it easy to stay updated, but you can drill down into specific accounts at any time. Plus, you can reorder your accounts' display, as well as have designated senders' emails go to the VIP mailbox so that they don't get lost in the crowd.
To format text, you have to select it to get the formatting contextual menu -- which many people may not realize. By contrast, Metro's Mail app automatically displays formatting controls when text is selected.