That is a hard decision. I used to have a AMD K-6 processor a LONG time ago, and ran around 768mb-1gb of Ram (those days that was a lot). It was pretty fast for it's time, but in today's world, I would choose processor over the minimal amount of RAM. Like was said, pick the fastest processor you can afford, and then just upgrade ram later on. Upgrading a processor on a notebook is a lot harder than upgrading RAM. RAM will the the more cheaper way to get a little bit of performance boost. Once you hit say 2GB of ram, regular everday use you won't notice a large increase. In processors, even on everyday use, you'll notice the increase, depending on how much you upgrade. If you go from 2.4 to 2.6, that's not much of an upgrade (saying if everythings' the same IE FSB).
TO choose between the 2, how much of a increase in processor speed your talking about?? If your talking about 1.8ghz vs 2.8ghz I would go with the 2.8ghz over ram. if your talking about 1.8ghz vs 2ghz, I would go RAM.