I have a Garmin Edge 520 and a Garmin 235. I've used both for cycling and prefer the Edge hands down. The Edge just mounts nicer on my bike and provides more information in an easier to read format.

The 235 is great for running and other activities. If you're planning to just cycling from time to time, but will spend most of your time running, hiking, doing weights, etc. I'd go for the 235. Otherwise a dedicated bike computer it is.