What metric do you use to determine "best"? If it is performance then the Core 2 Duo would be the winner while if it is bang for the buck then it may vary a bit. I would suggest a dual core laptop, e.g. Intel Core Duo, Core 2 Duo(which is the successor to Core Duo) or AMD Turion 64 x2, if you do any CPU-intensive tasks. I would likely stay away from Celeron or Sempron laptops unless you don't mind having a low power processor as these are for low-end systems which isn't the same as saying they use less electricity.
I'm planning on buying a new laptop soon since my current HP ZT3000's monitor does not work properly (works 1/50 times the laptop is turned on) so it's constantly hooked to an external and... well, no longer a laptop (costs around $600 to have it fixed by buying a new motherboard).
I remember when I bought a desktop 6 years ago I went with an AMD because they were generally cheaper than the pentiums, and performance-wise they were almost the same. With all this new intel dual-core, Inter core duo and AMD dual-core, I'm kinda lost now. What's the best option out there?