Some people like a choice.
Personally I can't be arsed with a smartphone of any type. A phone is what I make phone calls with. Anything else costs too much.
Sat Nav? I use a Binatone one I got for £50 from Asda, loaded iGo onto it and it's great. All in it cost a sight less than that silly Tom Tom thing. A friend has already sent his back because it kept insisting on sending him up dirt byways and private roads, it seems Tom Tom are useless in a rural setting. Tom Tom's curious answer was that he should update the maps himself* when he came accross these problems luckilly he bought it from a retailler with a no quibble 28 day refund policy.
I haven't tried Nokia's mapping, but I have tried it on a certain smartphone they gave me at work. It was frankly crap, which made the convenenience of having satnav on your phone somewhat moot.
* Can you imagine the OS trying that? "This landranger is innaccurate." "That's your problem sir. Just get your felt pens out and update it."