i like my edge 200.
it’s got all the usual computer stuff + simple route following – you plan course in garmin connect* and then upload it to your ‘device’ which then shows you a black line on the screen for you to follow – a bit like playing snake, with accurately displayed corners/wiggly bits.
(you can get proper sat-nav style navigation, but it’s not cheap…)
the edge 500 does HRM + cadence and stuff too, i think it’s got a barometric altimeter? – so the heights are a bit more accurate. And it’s got a wheel-sensor so you can still see your speed when you’re under trees, in a tunnel, etc.
(*Garmin connect is the worst website ever, but simple, reliable alternatives do exist)