I am comparing the Thrawn in Zahn's trilogy to Rebels and then this Thrawn.
Zahn's Thrawn is the smartest no contest. Brilliant strategist and long term thinker and also not really a full Empire supporter - he was much more about his homeworld and people. Rebels Thrawn was also pretty clever but definitely more of a dedicated Empire supporter. Ahsoka Thrawn just seems to be a groupie of the Dathomir witches (who should never have been inserted into Star Wars) who may or may not have some kind of plan to resurrect dead Dathomir but little else. I think part of the problem was waiting until Episode 6 to get to him. The show was too slow in many respects so that by the time we met the important characters there was insufficient time to both develop them and finish the story.