Chris Jericho by a mile. Jericho can cut the funny promo, he can cut the serious promo, he can do anything with his promos. The Rock, while insanely good at what he was doing in his promos, was always in the same ballpark with them, he was kind of one dimensional if you will.
This.
The Rock has always been the comedy trash-talker if anything really. Sure he had his moments of serious talks and all that. But he still resolved a lot to his popular and entertaining catchphrases.
On the other hand, Chris Jericho completely reinvented himself when he turned heel back in 2008. He wasn't using any of his catchphrases, he wasn't all loud and energetic. No he was simply a slow talking, condescending asshole. A true heel if you will. Chris has showcased that he can work the style of The Rock and Austin by being the funny entertaining guy on the microphone. But he have also showed that he could turn it into a complete revamp, a new Chris Jericho.