I have the Vizio Vtab as well, and tried Sygic. Sygic seems to be the choice for me as it does all you
Need, allows waypoint input for geocaching etc. But, I did not thoroughly put Sygic through it's paces, but you can try it free for 7 days, then it's $11.99. Also, Sygic does allow you to load one region. I loaded California maps at about 350MB's, and it seemed to work well down to a metre or two I think. Hope this helps, along with a very high rating on the market which is what always sways me, and is usually an accurate indicator of how good one program is over another.