The one question I have for YOU is this-
what size display?
A 10" screen is plenty big enough for any of the computer software out there to be usable. Smaller... yeah, not so much. I have a 7" in my car and a netbook with an 8.9" and both are too small for my normal laptop software (Delorme) to work very well imo.
I have found that Garmin Mobile PC works very well on small screens, but has a few disadvantages-
no on-screen keyboard
activation policy that makes it very difficult to migrate the software to a new system if you upgrade.
One of my BU-353s died, so I did get one of the Garmin bluetooth GPS sensors as well, and have to say that I am rather fond of the convenience of THAT, though battery needs to be charged every few days of use.
I have no experience with voice command nav, as I don't use that. Or even the spoken directions..