They're the same capacity and essentially the same engine. What provides the additional horses is something I've been trying to find out for a while. It could be anything from turbo pressure to remapped electronics - it'll be interesting to see if anyone here knows any details.
I'm intrigued by this too, many moons ago I drove a Peugeot 206 gti 180. At the time, Peugeot also had a standard 137 bhp gti, the 180 basically had a better air intake and exhaust system that gave it the extra 40 bhp, the 2.0lt engines were identical.
However these boys claim they can squeeze extra horsepower from an ecu remap or box that amends its settings
I'm unsure however I had the mk1 tt about 5 years ago. I had the 225 Bhp version.
This was almost the same as the 180 however it had a different engine map, plus the main thing was an additional inter cooler.
I wouldn't be surprised if its something like this in the q3 too