Mule cost - 50 energy ->50 energy and 50 minerals
Mule duration - 64s ->80s (total mule mineral return +50)
Mules would take a little longer to payoff , and killing them would be more rewarding
downside is, its harder to use and could feel less fun to mule hammer after surviving an attack.
upside (maybe) is killing a terrains entire worker line feels more punishing for the attacker