In theory, they would use a similar amount of fuel. All a turbo does is force more air and fuel into the chambers. At 6-9 BAR, you are looking at about 30-40%.
Now, at lower speeds when the Turbo isn't compressing, you obviously have a smaller capacity engine which should theoretically be more efficient but as Mega says, it depends on other factors. Do you remember when Top Gear races a Prius against a M3 on fuel consumption. Because the Prius was wringing it's guts out it managed 17mpg out of it's 1.5l engine where the 4.0l M3 returned 19mpg at the same speed.
Not a lot of help I know but I haven't a clue if you had a 1.4T and a 2.0N/A which is more efficient over all if they have similar timing etc. The 2.0 has more weight, inertia etc where the Turbo uses energy turning it and exchanges greater energy in heat and sound.
If I had a choice, I would always go for the lighter engine whatever the fuel consumption.