Destination vs. Source
In this step, Vista asks where you want to send the files you selected in the previous screen. If you have more than one paired device and want to select one that is not displayed as the default connection, you must browse for it. Windows then seeks connected and other devices in range.
The advantage here is that you could, if you needed to, set up a device from within the device browser by clicking the icon.
The Mac, on the other hand, has opened a Finder window where you can select what files or folder you wish to send. A folder can be sent uncompressed, unlike Vista's Bluetooth, which will only send a folder if it is compressed and handled as a single file.