keep in mind that both units can be mounted in a bybyte case that would allow for easy mounting in a double din opening. though the mounting brackets are slightly different for the 2 models, so keep that in mind..
personally, after handling a early led629, 669, and transflective 669, in terms of the lowest cost option, i would pick the HB 669 over the 701/629 because of the connection flexibility(i changed carpc mo.bo.'s after 3 months to a model that has vga, dvi, and hdmi outputs) and the fact that it is a brighter screen which makes sunlight readability easier. i feel the 669 is the best-cheapest alternative to a screen outfitted with the expensive transflective upgrade.