I agree with Dan, but I'd like to suggest a different way of looking at things.
How much is the money worth to you? If you are watching your budget, then you want cost-efficiency. But if the money is no big deal, then I would go for the RAM. Here's why:
The difference between "too much RAM" and "not enough RAM" is 2 years.
You might as well put in the extra while you can easily get it, if you think you'd like to keep your notebook for a good length of time. Right now, this is not cost-efficient, but in a year or two your RAM will be only ho-hum.
Of course, notebooks might be reckoned as having a lifespan of only a few years anyway. You want to think about that too. But extra RAM will certainly be a factor in extending the effective life of your system. It always has been.
So, returning to my first point: what is the money worth to you?