Well tomtom is very interactive and user-friendly. The design of the maps is pretty advanced. In contrast for examle nav4all does not have such highly interactive maps, which turns our as a drwaback especially in the navigation sphere.
Howver, nav4all could be cheaper from another perspective.
With nav4all the download per MB is not as expensive as many people think; and seond, it's up to you to decide how much you want to download.. I mean you live-steram the maps from the i-net and you download only the ones that you need; not a bundle of maps for a whole area. Thus you wouldn't have to pay for maps from the same area that you're not gonna use.. | 
TomTom vs. the rest 
Linear Mode
