The TomTom ONE XL Europe goes for approx. the same price as the 710, but has a bigger screen and a free RDS-TMC-receiver for traffic info.
Although I don't have a Dom Tom ( yet) , I was made to understand that the ONE XL gives the best value for money to date.
If you intend to visit the US , you'll have to buy the 910 serie, since that one got maps for Europe AND Canada +US.
I use a 510 almost on a daily basis in the UK and on occasion in France ,no problems as yet and the price has fallen rapidly. I don't know what the difference is between the 2 models, probably extra features.
I have a Garmin Nuvi 760. It is not recommended for a bike (guess cause it is not waterproof), but it works really, really, well. Y9u would need a headset of some kind to hear it on a bike however.