The best ones in terms of "netbook" seem to be:
1) Asus EEE PC 1015PED-P (N475, 1GB RAM, 6 cell), add 1GB RAM
2) Asus EEE PC 1015PED-M (N455, 1GB RAM, 6 cell), add 1GB RAM
3) Asus 1018P (N475, 2GB RAM, 4 cell)
4) Asus 1018PB (N455, 1GB RAM, 4 cell), add in 1GB ddr3 RAM for responsiveness

the next ones are:
Pretty much all the ones with N450 (most of them). They all have 1GB ddr2 RAM and similar 250/320gb storage. So the differentiator is whichever one is the cheapest or has the largest battery (# of cells) or is ergonomically the best.

I wouldn't recommend any of the dual core ones. They have half the battery life and only give something like 30% extra performance (equal to SU3500), so it really isn't a fair trade.

Since you've informed me you will be keeping it for ~5years, I would say a netbook doesn't cater well to your needs. With Windows 7, better newer programs will come out and in a short period you will regret getting a netbook because it will frustrate you.

Here's an example, Samsung Kies took 6minutes to properly sync to Galaxy S on Eee whereas it takes ~30seconds to do so on my Acer.

My recommendation would be to go with the Acer Aspire 4810TG. At the price I found you, it's a steal (mine cost $1700). I wouldn't be suprised if the other members on this site buy it before you do. Not only do you get something which is bleeding edge (seriously the only contender would be the Core i7 640-UM and ATi5650) but you get it in a decent package. It should last you five years even in this accelarating age.

But if it is out of your budget; get the Acer for 349 euros. You should upgrade to Windows 7 HomePremium (much speedier than Vista) and maybe upgrade to 4GB DDR3 RAM - to squeeze out all the performance juice. But that will set you back 100 euros and you miss out on the 4330 GPU- so you can only barely view HD videos.
But if you do not upgrade it, for 349 euros it is the same price as the ASUS Eee PC 1015PED-P and still much better.