I went with the CD ($169, in this case). While Magellan offers blank memory cards up to 64MB, the 32MB card ($55) is probably your best bet for use with CDs, since the largest marine chart on the one I worked with was about 24MB. I downloaded the chart for the northern-Bahamas area, covering Walker's Cay to the Berry Islands, and later, the chart for the Florida Keys area, covering Key Largo to the Dry Tortugas. Transferring each to the Meridian Color took about 20 minutes. Chart detail, which includes soundings, nav aids and information regarding marinas, fuel facilities and food stops, is impressive. While I worked with the greatest level of map detail, the busy Florida Bay chart took an average of eight seconds to refresh. A heads up: If you're using a memory card, you may find that detail of the internal map of North America is minimized.