When I bought my Garmin Edge 705, the prevailing wisdom was that you should buy maps on CD. I believe the thinking was that the CD version could be unlocked and used both on your PC and the GPS device. The MicroSD-based maps, on the other hand, could only be used on the GPS device. I ended up with maps on MicroSD, because I got a great price, and haven't found it to be a problem. Most of the PC-based mapping software I've tried gets map data from Google, so not having a CD-based map hasn't been an issue for me.