Yes, Google's map was sourced on public data and for the most part it initially stunk outside major cities. But that should be resolved in short order since their goal is that all corrections get responded to within 30 days, so that is a very ambitious correction timeline.
Tomtom's missed the boat by its slow response speed to user updates since the mapshare launch, however if you read between the lines at Teleatlas.com it appears they've been just too busy with the Teleatlas integrations.
They've been quickly ramping up their user-supplied map-correction capabilities:
map
825 - 50 thousand edits globally
map
830 - number of edits unnanounced
map
835 - 500 thousand edits globally
map
840 - 1.25 million edits globally
Map 840 is the first time I saw a significant improvement in my mapshare issues. So I have hope that Tomtom will catch up to the mapshare backlog soon.
I 'm guessing that the biggest issue in comparison to Google is the Tomtom delay. Currently, there is a 2-month delay in getting a Teleatlas Map into a Tomtom, and a much longer delay getting new roads into Teleatlas. So far, the fastest new road that I saw implemented was a December 2008 highway in Rhode Island that was implemented 9 months later in August's map 835.