Twenty inch laptop is much better for handling.

I recommend as follows,

1. 삼성 센스 NT-Q45A/C181 138 man won
2. 삼성 센스 NT-Q45A/W201 158 man won
3. SONY VAIO VGN-TZ17LN/B 217 man won

First and Second model from Samsung have similiar Spec and performance. The main difference is which graphic chipset it has. The second model have better graphic performance, but comsume more batteries.

ps)

SONY VAIO VGN-FZ15L is 15' laptop. It is also good. But in general, people don't prefer to sony VAIO.

c31lh / tz15l the models you said, are not Santa Rosa platform.