It depends what applications you'll be using the majority of the time. If you're using run-of-the-mill office apps and some games where redundant and predictable cache accesses benefit from the extra L2, the Barton would be the way to go. For multimedia and non-predictable ops, the extra clockspeed would be preferable. Personally, the 167MHz clockspeed difference and ~$40 price delta would make the 2400+ appealing, not factoring O:clock:'ability of course.
Chiz