I started with Eccleston when the reboot premiered in the UK and I found him remarkably dull. Tennant's episodes were, for the most part, nothing short of excellent, but he was too attractive for the role. He made the crazy, the intelligence, and the anger all...well, likeable. Matt Smith puts his feet further across both sides of the line - well until the last season, but let's pretend that one never happened, and while his eccentric nature is certainly more obvious and less socially acceptable, he also makes a far smaller deal about killing people who cross him. If anything, Matt Smith's my favourite Doctor purely because he embodies the Doctor's true self, and his own fierce denial of who he is.
Let's be honest. He's not a nice man. He can, and has, responded to military movements with far more collateral damage than they'd have caused, and justified it with "They were the aggressors." He's a madman and a killer, and where David Tennant made it charming, Matt Smith makes it frightening. Like babysitting a loveable child who murdered their parents.