Between those 2, got the Lenovo as they seems to be a better build. However sure you get a model with a 6 Cell Battery and not the 3 Cell. When the S10 was orginally released, it came with a 3 Cell Battery. They have now increased this to a 6 Cell Battery, however there is still some old stock in the market.
One word of warning. Do not mess around with the partitions on the hard drive. It will interfere with the one touch recovery process.
The only other netbook that seems to be populare is the MSI Wind. However my problem with MSI is that they go a little too crazy with Void If Removed Stickers, therefore you can not upgrade your ram or hard drive with out voiding the warranty.