I'm glad you put "IMO" and understand that this is YOUR opinion and may be appropriate for you.
I owned a 2012 GTI Autobahn (which I owed nothing on). I loved it about 95% of the time. I thought it needed just a little more power to be perfect and toyed with the idea of flashing the ECU. I'm glad I didn't because I think I would have liked the car less.
What I found most frustrating were the times I wanted to get into the power and the wheels would spin or ECS/ASR would kick in. I'm not talking about conditions with rain, snow, gravel (where the GTI's power was near useless). I'm talking about flooring the car from a standstill on anything other then a straight line on a smooth road. Not fun. I recall few times I almost got clobbered coming out of a T-intersection because ASR kicked in.
Enter the Golf R. From the 1st time I floored it I was sold. It happened to be raining at the time. Floored it...NO drama. Bumpy road...NO drama. I've been able to chirp the wheels....once. After a few days in this car I realized how much I would feather the throttle on the GTI to prevent wheelspin. So that 5% frustration was probably A LOT more, I just got used to it. I can't even imagine how frustrating a GTI with more power and torque would be.
As for comparisons, forget comparing a base GTI with a Golf R. Not the same buyer. If you're fine without leather, sunroof, HIDs, Dynaudio, Navigation, then R is not for you. If VW ever offers a base GTI with AWD then we can make some new comparisons, but until they do, the only real comparison is the Autobahn GTI vs the R and in MY humble opinion, AWD alone is worth the price. Automatic climate control, better suspension, better brakes, more power, better tune-ability, better resale, and exclusivity make the R a steal.