My 510 doesn't show a useful map, at least not with stock configuration.
I should rephrase my question: I'm not looking for routing necessarily, a "track" that has a line that I can follow is good enough.
What are the pros and cons of using Edge 800 vs. GPSMAP 64 vs. Etrex 30 for long brevets? What are the key features that make you feel one is better than another?
An BTW, how do you mount a GPSMAP 64 on the bike?