I own a 220 cdi so may be slightly biased, but equally I have driven a 270. I too loved the character and shove of the 270 despite its agricultural feel on startup. The one I have driven was being used as a courtesy car by my local MB specialist, and was a well used example that had covered 163k. Once I got it onto the A14 it became quiet, refined and super comfortable. the 220 is for me the ideal engine because it will do 45-50 mpg on a long run, driven sensibly, yet it has plenty of power and torque for cruising. My criteria, as one of the other posters has mentioned, would be to go for the later one, especially if it is post facelift, simply due to the greater likelihood of early issues being sorted. As far as the MOT concerns go, it would depend on what it failed on, and whether this may also be an indicator of a careless owner that might conceal other issues.