For a small difference or none in fuel consumption, I'd go for the model with a more powerful engine and better features. As most would say, there is no significant difference in fuel consumption between the 1.6L and 2.0L models of the Mazda3. I guess the same goes with the Focus but let's wait for inputs from more folks here. If you can chance upon the Focus TDCi, that will be the best option here (best combination of fuel efficiency, power, and lots of torque). Though if you want a compact with decent power and good enough fuel consumption, the Civic FD 1.8L will be another option though not a hatchback.