If it`s a good mix of the two,the diesel`s the best.
Power wise,well,the tax on the 1.6 is going to be less than the 1,8 & 2.0 (so`s the insurance).
Mpg wise you`d again probably better off with the 1.6 unless the car is full with a mix of people & goodies in which case eithe rof the other two.
I`ve a 2.0 and I get about 42ish round town & on runs I have had it up to 70mpg.
It really comes down to what you feel you can afford & the deal you can get.
I don`t regret getting the 2.0,as both the wife & I like the extra power that`s there if/when it`s needed.
MetalMicky ( Mike)
2004 2.0 TDCI Zetec