The cheaper one is the first iteration of the wave model. The 2004 model has a number of notable improvements.

1. Stronger plier pivot
2. Wider blades, safer
3. Multiple tool bits included

The old one is nice, but the new one will be stronger and more useful. There are also the titanium handled versions called the Charge Ti and the Charge XTi, that have better knife blade steel too.

IMHO it would be better to bu the new models, but you probably won't be unhappy with the old model either.