SLJ Quote
"Because Mace is who he is, we figure there's only one person in the universe who could defeat him in a lightsaber battle, and that would be Yoda, so my style is pretty efficient and I dispatch people pretty quickly and a modicum of flair."
From an Attack of the Clones interview from the Star Wars Vault.
There's another version of this on YouTube, but this is the longer version.
Since this is from 2002, SLJ jokes that it'll take Dooku and Anakin combined to take him down in EP3.
We should obviously take Ian's as well. They're more than voice actors.
My earliest "Star Wars vs" memory is my dad telling me as a kid that Sidious threw the fight with Mace and would have won otherwise. I've always been a supporter of that idea. However, if one actually looks at the history of the fight, it's very complicated. The original fight up until reshoots had Sidious blatantly throwing the fight with Mace. The fight was changed last-minute to make it far more ambiguous - so much so that it is said only Lucas knows the true answer with even the actors and team shooting the film left guessing. Ian maintains the stance Sidious threw the fight, but SLJ believes Mace beat him fair-and-square. Both stances are legitimate.
If one watches the fight, it's evident Sidious has the early advantage, perhaps even toying with Mace and prolonging the fight. However, McCallum is right that there is a shift of power in the mid-fight, and Mace does take the advantage. I find it likely Sidious threw the fight so he could lose on his own terms and time, rather than continue fighting further and risk a more unfortunate and likely deadly defeat.