Spoken like a true Gran Turismo hero.
Well, after reading this thread today I challenged my friend to a dual with both mentioned cars, on Forza 3 of course.
*all driving aids off, manual but not with clutch*
Tuned the ST up to 275bhp to match the claim by OP, and was forced to use the newer none bug eye impreza as the bug eye isn't in the game in standard or PPP spec but it was only slightly more powerfull so it had to do.
We tried 3 different tracks, Silverstone, Mugello, Nurburgring. On every track no matter who drove it the Subaru was the quicker car. It was also much better in the corners, with much more stability than the ST had. There wasn't as much between them on the straight bits but then whats so exciting about racing in straight lines? Silverstone for example I was almost 7 seconds a lap faster in the Impreza than the ST, consistantly.
I know that this test could be in no way a true reflection on either car in the real world, but it's gotta be not a million miles off as a lot of work did go into producing the game.
I know its all a moot point as the point the op was trying to make was that the Impreza just didnt feel as fast as the ST and for him he's right. I've driven several cars that have really underwhelmed me until i've looked at the speedo and been surprised (Audi TT prime example)
I'd love to own both cars at some point, but my sensible side says it'd be an ST long before it'd be an STi.