My recommendation is the TomTom, lots more value in the box and so easy to use!
I worry, maybe groundlessly, about some of the cheaper GPS packages and would like to be sure sure that map and software updates were easily available, POI files were of a well supported format, etc. Also of course, on a bike waterproofing is a sensible consideration (OK so you can put a plastic bag over it but I would prefer not to have to stop every time it rains).
I have a Tomtom Rider Mark 1, a Tomtom Rider Mark 2 and a Garmin 2720.
When the Rider 1 failed I bought the Garmin as I could not wait for Tomtom's awful repair service and I did not think much of it anyway. I now have a Mark 2 as well as Tomtom gave it to me as an apology after I complained that two months to replace the original Mark 1 was unacceptable.
The bottom line is that, although the Rider Mark 2 solves the mounting problems of the Mark 1, if I was buying again today it would be Garmin.
The Tomtom is OK for simple A to B and my wife is quite happy with the Rider 2 for that but has given up trying to understand their route with waypoint software, gets confused with its need to have a satnav fix to enter a route without having to go to a different menu option (Garmin manage without this), finds, as I do, the hit and miss method of zooming a map with the touch screen slider to fix a destination is a nightmare (Garmin have nice easy + and - buttons). The need to stop and change to night colours at sundown to reduce the glare is a nuisance (Garmins do it automatically). I can't say I agree that the software is "so easy to use" other than for the most basic tasks.
Garmins offer more "tweakability" for preferred road types for routes, screen data, etc.
Garmin's definition of Europe covers more countries than Tomtom's.
Garmin have Mapsource PC software which makes route planning on a PC easy with a one touch transfer of routes to the GPS. Tomtom have nothing to compete. Using "Tyre" software with Google maps is the nearest I have found but it's Mickey Mouse stuff compared with Mapsource and only works with a net connection.
Garmin's service is a revelation after experiencing Tomtom's eight weeks. When I broke my Garmin (my fault) it was replaced free of charge by return of post (and they sent a complete new retail boxed kit and I only sent back the satnav).
If value means cheaper then OK go Rider and it's OK for basic A to B. For a complete navigation package for bike and car I think Garmin win hands down.