When Mace Windu, Saesee Tiin, Agen Kolar and Kit Fisto turned up to arrest Palpatine only one of them was truly capable of winning that fight, even with a slim chance and that was Windu. He had Vaapad, a technique putting him close to using the dark side (or it was a dark side technique I cannot remember).
Palpatine did infact get the jump on the Jedi Masters using his skill with a lightsaber to slay three of them before coming up against one of the bets duellists in history.
Not only this but Palpatine shrouded his dark side movements, and blinded the council to the force.
I am however a firm believer that allot of the power of the Jedi was lost over the years leading to the rise of Palpatine. With many of their teaching lost (especially some of their more ancient teachings during KotOR 2, as-well as just before it.)
Kreia, knew allot more then she ever let on, and we never truly saw her true power I think, it was only on Malachor that we truly began to see what she was, her clever use of Telekinetic Lightsaber Combat, the proof of her subtle manipulations and the death of three Jedi Masters by stripping the force away from them. She also like Palpatine hid her movements, even Atris, who had by the time she met the exile again had fallen to the dark side did not notice Kreia, it was only later that she realised who it was that was accompanying the Exile.
TBH, they are both powerful. But Kreia may know allot of ancient techniques and secrets that Palpatine himself did not have access to and so my opinion is Kreia would win.