While MTW still holds a place on my HD I play RTW mostly because there is so much to be discovered. I haven't fought with all units yet and not al traits and ancillaries have been sen by me yet.

That being said, tactically MTW is better. While the more sophisticated system of the charge bonus, secondary weapons, shield etc are certainly in RTWs favour the AI let's it down big time. I'm a big fan of the opening skirmish. In MTW I spend more time moving my ranged units about, duelling with their archers then I spend fighting nose to nose with the main body. But skirmishing against RTW AI is like taking candy from a baby. Even if you stop wheeling onagers forward to pelt them till they quit the field with half their army dead. Or stop bringing masses of high qualitry slingers and archers.
And fighting with the main body of your army against theirs in RTW isn't much of a challenge either, though the only reason this is more noticable then in MTW is because now we get nice bonusses to put in the hurt. Let's face it MTW was no genius in this regard either, but sandwiching a unit in MTW only meant heavier morale penalties, it remained a slog until they broke because cavalry didn't plow in and ride down everyone with their backs turned like in RTW. In MTW cavalry were just a way to move swords about quickly, in RTW they really charge home.