1) 10,000 RPM (Rotations Per Minute) gets the data faster, so it's better than 7200RPM. It's worth it, but not many people get it right now.
You can also try getting the Maxtor MaXLine with a 16mb buffer. That's good too.
2) It's better, but it's not very useful right now. It'd be a very foolish thing to buy it right now, kinda like the DDR2 RAMs. Basically, just stick with the SATA 150.