OK I'm going to take a stab at this since I have not only player iRacing and GT5, I have been a road racer since the age of 17 and a go-karter before that.
First let me tell you that I have been a consistent top 5 racer in SCCA for years now with multiple podium finishes and race wins as well as a driver for a race winning 24hr endurance race team SO i would like to think I might know a little something about real racing and simulators/video games lol but this is only my opinion.
I have raced karts, shifter karts, formula cars (multiple) and of recent spec miata in SCCA.
I have raced multiple times at 11 different road courses in the USA but my favorite is lime rock park.
When I first heard about iRacing and it's great reproduction of the real tracks, I was VERY excited.
BAMM I take my spec racer (spec boat as we call them) and head to my home track of Lime Rock Park.
They're recreation of the track, graphics aside, was superb. Every bump and patch, every quirky tricky part is there.
So after 3 warm up laps I start going 9 tenths and I realize that, for as great as the track recreation was, the vehicle DOES NOT respond properly. CAR PHYSICS AWFUL.
It was flat out awful. Every input is exaggerated and it simply took all the fun out of the game, but more importantly, the car did not behave to setup as I had hoped.
So I figure hey it's me, so I spend endless hours playing with wheel settings and car settings. OK getting better but still doesn't feel right.
So I go and buy a Miata figuring well maybe it was the spec boat. WRONG. I couldn't in any way duplicate inputs from real life to the game. Not even close.
At the time in real life I could lap LRP in the 1:02's and I couldn't break into the 1:04's.
I put the game down and have yet to play it again. EVER.
It was frustratiing and had zero fun factor when people barely tap you racing online and you go violently spinning out of control yet in real life we bump draft at 130+ with no issues.
In iRacing's defense, the biggest part of piloting a race car is what you feel in your butt cheeks and that's something a video game on your TV or computer screen cannot duplicate, but they're car physics are so off that it's not worth my time.
Then GT5 Prologue comes out and I couldn't put it down. Lost half my life playing that game and the other half is currently being lost lol.
I love the almost endless database of cars, but more importantly I love how the game feels.
Miss your entry point by 2 tenths and the car understeers and goes off the line forcing you to slow to stay on the track. Add a little downforce and bamm the car feels better in a sweeper. Everything with the car you are piloting just feels and reacts as it should.
Now, combine GT5's graphics and car physics to iRacing's tracks and you will have a huge home run on your hands, but I think it says a lot that I have maybe 5 hours of iRacing under my belt, mostly playing with wheel and car settings, compared to hundreds of hours of GT5 and race cars have been my life since I was 9 and in a gokart.
Hope this helps answer some questions and hope to race some of you some time soon, in GT5 or in real life
