Did you ever fine the info?

From the various articles and tests I've read, among the
A3/GTi and A4, even though they all share the 2.0T FSI there are some quoted differences.

The GTI/A3 use 10.3:1 compression vs. the A4's 10.5:1
The GTI/GLI/A3 list the redline at 6500rpm, even though the rev limiter is closer to 6800-7000rpm, whereas the A4 lists redline at 6800rpm and goes past 7000rpm to fuel cutoff.

The GTI/A3 use a single front mount intercooler, the A4 uses dual side mounted intercoolers.

Early testing on the GLI/GTI showed somewhat slower performance with 0-60 in the low 7's and 1/4 mile in low 15's. More recent GTI/GLI/A3 testing have shown performance in 0-60 from 6.2 (DSG) to 6.7 with manual.
1/4 miles times around 14.7-15.1.
Seems the 2.0T has been bumped somewhat as performance is quite amazing and dyno's have been reading high numbers compared to printed crank numbers.

The A4 with 2.0T and quattro is about 400lbs heavier, yet the performance numbers have been nearly the same as the GTI/A3 and that is very surprising considering the weight and added drag of AWD. That last Road & Track AWD comparo rand an A4 2.0T quattro manual with S-line, and it won.
0-60 was 6.5 and the 1/4 at 15.0
A previous A4 2.0T quattro manual no S-line ran similar numbers, 0-60 at 6.4 and the 1/4 in 14.9.

Seems the A4 2.0T FSI may be a bit higher rated and that could be due to it's higher compression ratio and greater redline.
The A4 quattro shows it's weight once speeds get to 90-100mph where the lighter cars take the advantage in time to speed.
Also, take a look at the chip tuners and you'll note that the
A3/GTI chips give a GREATER increase in power vs. the A4.
I"m not sure why, but my guess is that the A4's higher compression may be a limiting factor.