Comparing across different systems starting from the BIOS splash screen is not a good idea. Each of those computers has different components that take different amounts of time to initialize, and can cause significant variance.
You should only compare to the exact same system to prevent these kinds of variables from giving you a false impression about the actual speed, which I'm betting is what's happening here.
Instead of measuring from the splash screen, stop each computer at the boot menu (where you choose what device to boot from), and measure from the time you select your hard drive. This will avoid accidentally including time totally unrelated (and usually uncontrollable) to your OS or SSD.