I just gave a quick look to the two M8s as posted on the Treefrog website. Obviously a size comparison isn't possible from the photos, but I'll bet they are very close (if not the same).
Old version has all four crewmen visible, with the drivers poking out of opened hull hatches. Minimal stowage. Not radio aerials visible.
New version has the front hatches closed, new figures in the turret, an infantryman on the rear deck and some stowage on the aft end with an orange aircraft recognition panel showing. The vehicle in the photos has wire radio aerials.
Both armored cars have the extra ring-mount for the .50 cal MG, a modification common in ETO, but rare elsewhere.
So, so some nice differences. I like the drivers showing, but I also like the stowage and the new turret crew poses.
Gary