Some of the decision will depend on the kind of vehicle you drive, and how much space there is for a computer. One thing you might consider is a built-in but surreptitious screen -- the sort you have a cover on or a disguise on top of -- for those parking situations. Then you could choose whatever device you like and use the vehicle monitor as an external device.
But, if you're going to that trouble, a built-in carPC, installed out of sight, would work just as nicely and might cost less. I've been running with a laptop in my car for some time, and I decided a built-in unit is much more to my liking because it seems as if fooling with the laptop -- effectively reinstalling it for every use -- just became a pain in the behinder.
Still, I'll have well over the $700 price of the Wibrain invested, plus hundreds of design and building and tinkering hours (plus almost as much time cruising MP3Car.com).
Maybe, if you wait a while, they'll produce a big-screen Wibrain . . .
If just enough is really good, then too much ought to be perfect.
2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html