The best thing going is an iPhone with the Navionics carribean app. It has a google earth overlay. The Garmin Bluechart G2 Vision charts are a joke by comparison. I have both and reach for my iPhone every time when going back and forth to the atolls. I felt pretty suckered buying a fancy touch screen chart plotter for big bucks only to have my iPhone blow it a way, in detail and accuracy.
Simon is right that none can be relied on for navigating channels ,avoiding navigational hazards, etc.. Great for marking spots, zero visibility and dark overcast nights (when no other aids exist) Belize is funny sticks are the main navigational markers, but be careful some you follow and some you need to avoid.