I think that you are drastically underestimating the difference in ability between the two characters' opponents.
Qui-Gon was an old man. During the first fight with Maul he is winded after only a few blows. Kenobi in TPM was still only a padawan, if an advanced one. The two used a method of fighting poorly suited to their environment, and were fighting the first known Sith in millenia. There was not much call for practice against other lightsaber wielding foes.
Anakin and RotS Kenobi, however, were both in their prime. They both had a lot of practice against other Force users, such as Dooku or (in The Clone Wars, Ventress) as well as melee combatants like Grievous and his Magnaguards. In addition, the two were intensely familiar with each others' styles. They were both powerful enough to be on the Council, Kenobi legitimately and Anakin was at least plausible as a Master.
Kenobi's oldest incarnation was significantly more powerful and experienced than his younger self, but still stood no chance against Vader. (The environment was the deciding factor there, not skill.)
This really isn't even a contest.