I've got the 1.8. I wanted a 1.6, but they were in very short supply when I got the car. In fact the dealer lied and said it had been discontinued!
The 1.6 is generally the better engine. The 1.8 is quite rough and noisy at low revs, and doesn't give very good economy around town. It's an excellent motorway cruiser though, and is 20% more powerful in the mid-range of revs than the 1.6
I think the only thing that really gets me is the economy around town. It's appalling if you only do short trips because the engine takes an age to warm up.
I've not driven the petrol versions, but I've read the 1.6 is underpowered for the size of the car. All the petrol versions are quite thirsty, allegedly.
i have 1.8 petrol which averages 22 miles to the gallon i actually took it back to dealer and was told that nothing was wrong and that it was doing around 27 miles to the gallon which is not what ford figures state it should do