Generic GPS Devices

I was thinking of getting a new GPS to update my old Navman which was made in 2008 and has outdated maps now.

Upon searching ebay I have seen many generic, china branded ones which appear fully featured and seem reasonably priced. I was just wondering whether anyone has any experience using them and what sort of mapping software they use? If it is merely just running Gmaps on a low quality tablet then I will stick to my phone as that can do the exact same thing. It seems they might just be selling a low end $30 tablet with the added mount and accessories.

7" tablet style model > currently on sale…claims to be "ebay's most functional GPS system"
http://www.ebay.com.au/itm/7-inch-GPS-SAT-NAV-Car-Navigation…

5" model > product description is more detailed but still doesn't give too much away
http://www.ebay.com.au/itm/New-Cylink-Car-Sat-Nav-GPS-Naviga…