If you can't see any difference why are you worrying?
If you must test them the simplest thing to do is when you have booted your computer run each browser once with the same home page then time each one starting up from the first click on the icon to fully loaded. You will now know which loads fastest.
Next with the browser open see how long each takes to open a new tab. With a new tab open and empty see how long it takes to load a page fully from wherever you like but use the same with both browsers.