They are the ultimate team.
One one hand, you have the massive green monster that cannot be stopped by any of Farquaad's minions. He would rather "settle this over a pint," but those minions know better.
Instead, they get all offensive trying to drive Shrek away from Farquaad, but his massive body just sits there. Any would-be escape route for Farquaad is gone. The only thing in sight is a 300-plus pound wall of green flubber.
Puss is more of the finesse attacker. Sure, he has the strength to pull any stunt off, but he would rather just toss those minions aside and give them a good swing of his mighty sword.
He's much more agile than his counterpart. He's a lot quicker than many of his opponents as well. This gives him the ultimate edge. He also has that wicked cute smile that would stop any invaders in their path to glare in awe. This, in turn, only causes those poor souls to get trounced on.
The unfortunate side of all this—Puss was caught once with that "catnip" by the guards of the castle. Shrek also seemed to be involved in this operation. Let's hope things go their way so that they can continue to drive back those damn minions and get to their ultimate goal, Lord Farquaad.