Air won't take you to 4.8GHz on either chip unless you get a seriously rare stepping.
For the most part the 9X on the 8400 will do just fine. Not worth the extra bucks I think, but then again if you are into that sort of thing looking for 4.8GHz then it may be worth it.
For the most part the 9X on the 8400 will do just fine. Not worth the extra bucks I think, but then again if you are into that sort of thing looking for 4.8GHz then it may be worth it.