As you all know, I have a 2.5TD Elite.
Being 6 cylinder, it will always be a smoother engine than the 2.2. In standard form, its awful. Chipped makes it more drivable, and economical. However, I would not recommend an auto with this engine (even ar35) - it loses so much power through it.
The short oil changes are no problem, as you want to be changing diesel oil every 3k anyway, due to the particulates.
No small TD will have lots of torque low down, as its utterly reliant on the turbo.
The BMW unit is not as good as uneducated people think.
The 2.2 seems to have its fair share of reliability/performance issues.
My advice - find one you fancy, and test drive it.
BTW, I have found the V6 to be very reliable, no niggles, with only one breakdown in 4yrs of ownership (rather crank sensor), which makes it most reliable vehicle I've had.