Well, im just working with very limited knowledge, and wookieepedia, so i cant give anything better.
Well, you don't have to say everything thats possibly relavant, just some of it mixed with some logic. For example-
'I think Dooku would win. He has demonstrated duelling skills in excess to that of Kit Fisto, his opponent, in that he's held off both Anakin and Obi won at once and given Yoda a decent fight, both of which are superior to Fisto's duelling feats. He has also shown greater force powers, giving Yoda trouble trouble with his lightning, splintering a roof and disabling Kenobi with TK, as well as being named one of the greatest jedi ever (or something) and an even better sith etc'
I think that Yoda was holding back because he though maybe Dooku could be saved, and it happened to happen later that Dooku would say that he wished to convert sides, and asked for Kenobi and Skywalker to come to Vjun and pick him up or start negotiations, and Yoda went to in the hopes that Dooku was sincere. He wasnt, and Yoda gave up on his former student.