Probably something to do with VW using 197 of the TFSI's horses, as opposed to SEAT who managed to get 225 stalions out of the 20VT. I'm guessing here but 197 is less than 225. QED.
You'll have to wait for the hotter Golf GTI coming next year before its the other way round, but even then, it'll still be ~9 horses short of the new Cupra.