-Armadyl Godsword:
The Judgement.
Inflicts 25% more damage.
50% Special bar drain.
-Bandos Godsword:
Warstrike.
Drains an opponent's combat statistics by the damage hit. Statistics are drained in the following order: Defence, strength, prayer, attack, magic, ranged. An extra 10% is added to the inflicted damage.
100% Special bar drain.
-Saradomin Godsword:
Healing Blade.
Inflicts normal damage, but restores half of the damage to the attacker's hitpoints and a quarter to their prayer. Players will receive a minimum of 10 hitpoints and 5 prayer.
50% Special bar drain.
-Zamorak Godsword:
Ice Cleave.
Freezes opponent for 20 seconds, but they can still attack.
60% Special bar drain.
I would have to take Saradomin Godsword as the best Godsword. It is capable of healing you and restoring Prayer, this could out rule the need for Guthan on certain occasions as well as the need for Prayer Potions and food. Unless you're pking all the time, I'd grab the SGS.