Syscom,
Yes the Germans emphasized protection a lot, but while certainly important it is far from a halftracks only job. The American design emphasized using as small amounts of plates as possible and made sure that weight was kept low compared to engine power, which is also good, and productivity high.
The only real critizism I'd give the American desgin was the actual track system used, it offered far too little traction and gave to high a ground pressure. To try and compensate for that they powered the front wheels as-well, but it made no difference as they have no traction in knee deeb mud and thus provide no help at all. The Germans instead left the front wheels unpowered and made the tracks much larger, concentrating all power to the tracks, this gave better cross country performance.
Interestingly Wikipedia states otherwise and claims that the powered front wheels were an advantage and actually also claims that the German halftracks were less mobile.