1.)you can power up, just before you´re attacked and your enemie don´t know, if he chose the right victom :devil
2.)you can regenerate health and ki, eat a bean, search the right position for your new attack,...
it has more tactical advantages
would you play cs, if everyone has a radar with your position, your health and your weapon(enemy-team, i mean)?
ok you can play esf like q3, just kill until you´re killed, but that´s boring and esf would be nothing more than a weapon-mod, which enables you to fly