For working out where you are, they are all fairly good - the one feature that impresses me is Trafficmaster's call centre where when they've directed you down a narrow lane that no sane person would travel down you can contact them and yell at them and they'll remove it from the list of recommended routes. (The ability to phone them up after your car's been nicked and get them to turn on the GPS monitoring (for a fee) and relay it real time to the police is another fun one).

In terms of networks, they all are pretty much alike and I think the features are similar. And never having used them directly I can't speak about reliability.