In general, while I do see the gap in power between ROTS Mace and ROTS Obi Wan as significant enough for a decisive victory every time, I don't see a single reason why TPM Mace should be awarded the same honor considering that he would be vastly less powerful than ROTS Mace. Having more than a decade to grow in power, and 3 of which are spent in a period of constant war, and considering his massive potential which likely rivals that of Sidious's and the fact that his style of combat is based on drawing strength from his emotions i.e. skirting the dark side and considering the fact that he is still relatively young around TPM, means we would have to ignore a great deal of thematic evidence to not conclude at the very least, a pretty substantial difference in power between TPM Mace and ROTS Mace.
Even if I am generous and give Mace the power edge, it is equally obvious that it is small enough to not matter at all, considering Jedi restraints and I am not aware of any skill based showings that TPM Mace has that place him anywhere near ROTS Kenobi in lightsaber combat. That and considering that lightsaber combat is what primarily determines the outcome of duels, I am not seeing why Kenobi doesn't take the majority.