This all goes back to the classic Intel vs AMD debate where there is no real right or wrong answer.
As far as I know, the AMD chips are better performers and better value for money than the Intel chips but the Intel Pentium M (Centrino) is better for power consumption if battery life is a major factor (and still performs very well too).
As for RAM, 512MB will be suitable for the vast majority of todays tasks. It depends what your using the laptop for and how long your planning to keep it as to whether or not you should upgrade to 1GB. It would be worth asking the manufacturer whether or not you can upgrade the RAM at a later date.