Having seen the advantages on other systems (e.g. Linux) with regards to programs being compiled specifically for the capabilities of the machine it is installed on, it became obviously clear that Windows users were at a disadvantage:
Mozilla only releases windows executables with maximum compatibility in mind, meaning that Firefox is made to run on as many different systems as possible, sacrificing efficiency and speed in the process to be compatible with, by current standards, absolutely ancient hardware (backwards compatible to the first Pentium processors from 1993).