None are perfect, they all need to be used with a handful of common sense.
I use Garmin I3 and Garmin nuvi 350 which I'm very very happy with.
Tom Tom have a lot of followers but to many gimmicks for my liking and I and friends have found turn warning etc not to be as good as the Garmins. Kevin on here has had probs with a new nuvi 360 and I know others who like me swear by them. They are part of mass production chip industry so you can get the odd rogue units from any brand. as you can with a PC. Garmin Help desk is very good and www.pocketgps.co.uk forum will answser vitualy any question you may have.
Garmin have a very easy to use PC update system, you just connect follow easy instructions and regular updates to the operating system are done automatically and mapping can be updated FOC when new map ap dates come on line.