i have never heard of the 3200 being able to do telenav/navigation. im sure it's like the katana you could do it, but it's slow being vision.
here's the difference, let's say it does work, you'd pay 15 for the vision pack and then pay 9.99 to telenav separately for the 3200.
on the m510, you'd pay $20 for the Navigation Power Pack. and it'd be much faster. not only are you saving $5/month with the 510/dlx, you are getting more features - video, video mail, power vision, sprint tv, sprint radio, nfl network, music store.
used to work for sprint. now i just torment them. here to help and judge your posts