Which processor?

[Kitwn]

This is one for our experts who understand which features of a CPU PRE uses most:

I'm looking at laptops suitable for editing video (mostly SD PAL here). eSATA is a must, as is a good size screen (15.6" minimum). I'm not bothered about light weight or long battery life, the ability to do the job is all that matters.

Most in my price range are either using an Intel i5 430 dual core CPU or, less common, the intel i7 720 quad core. The former clocks at 2.26GHz and the latter at a 'mere' 1.6GHz. On possibility uses an AMD phenom II dual core chip clocked at 2.8GHz.
To add to the confusion there are variations in L2, L3 cache etc. and options on graphic cards as well.

Can anyone explain the relative importance of the various chip parameters with reference to editing using pre and pse (v7 if it matters)? As usual I'm overwhelmed by the number of options and choices that need to be made posting.php?mode=post&f=4#

Kit