Sidious, Yoda, or Plagueis?
Another issue I have with Darth Powers' assessments.
Yoda was wounded at one point by an amped Dooku, given Dooku eventually saw himself loosing even when feeding on the resonant dark side energies of Vjun, Yoda just couldn't match Sidious. The dark side has many advantages over the light in terms of offensive powers. Yoda was slightly more powerful than Sidious in terms of raw energy but couldn't best the latter due to many factors regarding their abilities in battle.
To that, I stress that when peak Sidious, one not out of practice as he was when he faced and eventually was defeated by Windu, fought alongside Plagueis and no indication was made that the apprentice was in any way more ferocious than the master. In fact, quite the contrary.
Sidious did wait until his master was incapacitated to attack, though that is his way and this in and of itself is no indicator of the master's superior abilities. They were, however, equals in power and this is stated many times throughout the novel. Plagueis demonstrated many abilities that Sidious did not in all the EU, his ability to "atomize" his assailants with Force wave stands out the most.
I'd say Plagueis is second only to NJO/FOTJ Luke Skywalker.