Which NAV radio is best to buy?

I have a 2009(New Style) Silverado that has BOSE and 6 CD-radio. Here is what I want to do.....I want to install a NAV radio. I have 3 options: Factory, Advent OGM1, Rosen Entertainment. Which is the most used/recommended/drawbacks. I also wish to us the Coastal Entertainment/TVor Nav2go adapter to add extra cameras and I know that is for only the factory radio. Anyone got advice?

probably the one you don't make 2 threads about

I am searching for answers, not smart comments, thanks.