A massive increase. I have a 7200 RPM drive in my portable hard drive and it takes a lot less time to add files to it than my laptops 5200. 5200 is good but avoid anything less as it gets to be silly in terms of transfer times. However one thing I know is that 7200 drives eat more battery than 5200 for obvious reasons so consider how you plan to use the drive. Depending on the size of the drive the £50 sounds a bit on the expensive side.