None of them will give reliable A-B routing over a distance of more than about 20-30km - so your daily plan-ahead should be composed of 3 or 4 hops. Depending on the package you buy, you may have to factor in the cost of adding maps into the GPS.
Why is it that they can’t auto-route over a decent distance? This is frustrating for me. If I go for a ride, get lost or otherwise end up in an unexpected place, and just want to head for home 40 km away, they tend not to work. The eTrex 20 can grind away for literally 10 minutes (during which time I freeze) and after all of that still throw up an out-of-memory error. The Edge 800 is a bit better (faster) but still often takes several minutes to produce a route and often fails. It may not help that I’m usually not far from the vast road network of Paris.
My 2012 iPhone throws up any route instantly (and guesses the right road if I mistake a
boulevard for a
rue), but maybe that’s not a valid comparison. More gallingly, my 2008 nüvi spits out a route in seconds. The nüvi is a low-cost, in-car sat-nav made by … Garmin.
The eTrex and Edge also suffer from having character-limited input fields for things like road names. Sometimes I have to give up entering an address by name and just zoom and pan and zoom and pan and click on the stamp-sized map display to select a destination. Neither the eTrex’s joystick nor the Edge’s non-multi-touch, non-capacitive touchscreen works very well for this. Of course map redraws also take an eternity at some zoom levels…
By the way, I have found that paying for Garmin City Navigator maps makes auto-routing much better, i.e. just about usable (with the above restriction on route distance), whereas with various OpenStreetMap-based maps I could never get auto-routing to give sensible recommendations, no matter how I fiddled with the routing options.