In point pvp you have unlimited lives and must try and acquire the most points within the time limit.
S units are worth 5 points/A units are worth 4 points/ B units are worth 3 points/ C units are worth 2 points.
In stock pvp you have a limited amount of lives, once you run out you can no longer respawn, whichever team survives wins.
S units have one life and 3/4 (or half) meaning they respawn the second time with less health/ A units have 2 lives/ B units have 3 lives/ C units have 4 lives.