Being a Tomtom user, same as most mates, I recommend Tomtom.
Gave it to my 75 year old father to travel interstate.
He got around just fine. If he can use it anyone can.
Is simply the best choice for ease of use (user friendly)
Navman might be also, but I wouldnt know.
All reviews I have read rate Tomtom as the standout.
If you dont need extra features get Tomtom One V3 at just over $300 is a good buy.
Or if you want too pay more for the extras tryTomtomGo.