Posted 01 October 2012 - 09:37
If money is not a problem, buy them all. Some GPS programs have better maps for half places, other programs have better maps on other places.
I use 3 programs, one is good for my city, another is better for the capital city, the 3rd one is great for suburbs, villages and islands in my country. The 3 programs use map providers TeleAtlas, GI and NAVTEQ respectivelly. Always check the map providers first (and their coverage in your area) and then the program itself.
If you buy the best program (TomTom for example) and you're in a village where TeleAtlas (TomTom's provider) doesn't have any map data, then the program is useless for you.