Generally, newer BIOS will help in regard to newer hardware, i.e. say, a new HDD or new RAM running smoothly, quickening boot up times, etc... It isn't necessary, especially on a laptop, which isn't readily upgradeable, but it does help to a degree.
Add support for some newer CPUs, fixes to stability problems, ..., etc.
Sometimes the motherboard manufacturer will even list the changes made for each BIOS revision.