So because a weapon is quicker, it's better?
Fire axe is a much more powerful weapon and can be used into later waves if you are a skilled beserker, while the machete has a tough time against clots.
where did i say that counts for all weapons? machette can take a husks head off with one blow on alt fire most others can be done with one excluding sirens/fleshpounds, etc
then again you get mobbed by a few crawlers i dont think the fire axe is going to save you anytime soon