I'm not sure it is objectively marginal. At Circuit of the Americas where they have both raced recently the difference in lap time is about 10 seconds. That doesn't sound like a lot but is close to 10% of the lap. The F1 race is 56 laps so by the end an Indycar is going to be 5 or 6 laps down. Throw in the fact an Indycar can't do 56 laps without refueling and it might be closer to 7 laps. In motorsport that is extreme