Once again, it depends on the usage. A hard disk with 5400 RPM will be lighter and slower in transferring data as compared to the 7200 RPM but it will also cause less damage to your computer.
Ideally, you will not notice much difference when you use your computer, laptop or desktop, for general purpose. If the slight difference in price does not bother you, you can go for a 7200 RPM hard disk drive. This will also fetch you a higher resale value for your laptop.