Just sharing that it's unlikely you'll feel the difference with just what you've listed. I'm currently using the following for some various works.

Laptop 1. p3-600, 256MB
Laptops 2, 3, Athlon 64, 512MB

The MySQL server is running on the p3-600 and I do the initial VB6 app on the smaller laptop. It gives me some idea if there will be a performance issue.

At demo time, the p3-600 still holds the MySQL server, but the newer laptops make for a better presence during the demo.

Also holding other dev tools such a Palm's PODS and a collection of cross compilers, none of the machines seem to strain at all.

I'd lean to the laptop with the better screen and keyboard.