Aesthetics is the biggest difference. They're close to the same size and same weight. The blade on the 4200 is a bit thicker, but the 5000 is no lightweight either. The 4200 has G10 overlays to improve grip, but I can't imagine anything grippier than the 5000's handles with their agressive contouring.
Apart from looks, it's hard to say which is better, without handling them yourself. Even if there's no local shop that has either, there might be one that has a 520 and a 420, which are the non-auto counterparts (but otherwise basically identical).
This might sound odd coming from an auto enthusiast like myself, but I happen to find the non-auto AXIS lock Benchmades more useful than the automatic ones. If you pull back on the AXIS lock on a manual, you can flick your wrist and the blade comes out easily--basically like the auto does (just inertia assisted rather than sprung). However, with the manual ones, you can close it the same way. Can't do that with the auto AXIS's.