Placidity
Chief Executive Officer
Palpatine faking defeat to create a golden opportunity for Anakin to fully turn to the dark side is a sound and possible theory.
However it doesn't mean Mace couldn't have beat him anyways. After Palps lost his saber he tried to blast Mace with force lightning, I believe when he did that, he was trying without reserve to take Mace out. I think if Palps could have killed him earlier, he would have, but he knew he couldn't and then MAYBE the theory that he faked defeat comes in later when Anakin arrives.
Still I don't think Palps would take such a great risk of depending on Anakin to intervene. Sure he has spent much time and effort in corrupting Anakin and he probably has some foresight into what will happen, but foresight is not 100% accurate and things can change. Palps knows this, so he is still taking a big risk nonetheless, this fact reduces the credibility of the 'faked defeat' theory. I'm sure theres also many other arguments against it.
Anyway, on to another point - Mace Windu has always been regarded as one of the most powerful Jedi. Anakin describes his master, Obi-Wan as "as wise as Master Yoda and as powerful as Master Windu". Obviously Obi-Wan is no where near them in power, but the fact that Anakin used this comparison gives insight to what level Mace Windu is at, apparently in the same league as Yoda. In light of this, I would say Mace Windu would beat Palps if they ever fought again.
Also, I'd like to add that the only reason Palps stalemated Yoda is because he switched the fight to a force battle. If Yoda could've forced a saber fight, he would have eventually killed Palpatine. Even if Palps switched to using force lightning against Mace Windu during the saber fight, it wouldn't have matter as we saw in the film. Unlike Yoda, Mace Windu's vaapad style (a lightsaber style/discipline that allows the user to redirect attacks at his/her opponent) allows him to withstand the lightning.
Also, personally I think the dark side is more powerful, and Mace Windu makes use of this.