New battery or netbook ?

Hi everyone.

I got a 10' Toshiba L670-105, a 17" laptop that i bought for university (My laptop is quite good, with an i5, 4 Gb RAM, 640 Gb HD, and a good graphic card) . After 2-3 weeks i gave up taking notes on it, because battery life is... bad. I barely reach 2h with it, and i got about 4-6h of lessons in a day. Now it's my home computer.

But now, i want to come back in lecture halls with a laptop. But i want your opinion. I'm considering to buy a new battery, a 12-cell battery (i'm on a 6-cell) to have more battery life, or buy a netbook.

It is the netbook the best solution ? Light, good battery life... but not very powerful. So, what's your opinion ?

And oh, i don't really want a tablet. I was thinking of Asus Transformer Prime, but i want to run on Windows.