The 2.2iCTDI is pretty good as diesels go. It's chain cam, so no belts to replace every four years, and no diesel particulate filter to worry about. You'll probably get 5mpg better than the 1.8iVTEC. And, of course, more torque. So, if you're ever towing, no contest. Day to day, it's hard to call. The 1.8i handles better because the engine is lighter, so it's the sportier choice. What would do it for me would be the fact that the 1.8i comes about £1500 cheaper than the 2.2iCTDI.