head to head
iRacing asks more than Forza Motorsport 7, and the gap is reads.

Execution · Practiced Mastery
Consistent lap-time precision supported by tuning and racing-line study.

Execution · Practiced Mastery
Hardcore online racing sim with PvP wheel duels.
Forza Motorsport 7 leans Execution (Practiced Mastery); iRacing leans Execution (Practiced Mastery).
iRacing leans a little harder on execution, though the gap is small.
Forza Motorsport 7
Braking points, throttle control and racing lines are everything
iRacing
Brutally precise wheel inputs required
iRacing leans clearly harder on reads.
Forza Motorsport 7
Online racecraft adds light human positioning play
iRacing
Serious wheel-to-wheel racing vs humans
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Forza Motorsport 7
Dynamic weather shifts conditions mid-race
iRacing
Weather, tire wear, mechanical variance
iRacing leans a little harder on optimization, though the gap is small.
Forza Motorsport 7
Tuning setups and line study reward engineering effort
iRacing
Setup, strategy, iRating progression
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.