Kenobi's main strength was his use of tactics in battle, he relied on them more than anything, but when it comes to raw power, Anakin was always better.
"Obi-Wan let go. Of everything....And their lightsabers. Startled, Anakin instinctively shifted his Force grip, releasing one wrist to reach for his blade; in that instant Obi-Wan twisted free of his other hand and with the Force caught up his own blade, reversing it along his forearm so that his swift parry of Anakin's thundering overhand not only blocked the strike but directed both blades to slice through the wall against which he stood. He slid Anakin's following thrust through the wall on the opposite side, guiding both blades again up and over his head in a circular sweep so that he could use the power of Anakin's next chop to drive himself backward through the wall, outside into the smoke and the falling cinders."
"Obi-Wan let Anakin drive him toward it. It was a place, he decided, they should reach together."
*I won't quote the mechanical hand incident since it seems you already know about it.
"Anakin kicked off from the toppling superstructure, swing through a wide arc over the lava's boil. Obi-wan shoved out and met him there, holding the cable Anakin flicked a shien whipcrack at his knee's. Obi-wan yanked is legs high and slashed through the cable Anakin's hand, and Anakin fell."
It wasn't until about the halfwya point of the fight did Obi-wan release everything. Obi-wan was the better maybe not the stronger but the better of the two. He was smarter, more patient, etc.
Power isn't just strength and ability. It is also smarts and tactic. If it was Strength and Ability then Obi-wan would have lost so many fights. Its just not Obi-wan's way. If it was, he would have lost to: Anakin, Grevious, Maul, Durge, Ventress and, others.