Word on the street is that 1LE track times are better than the ZL1. And the ZL1 doesn't have time to take advantage of the super charger. Also, the 1LE doesn't suffer from heat soak as much as the Mustangs, so the 1LE wins on longer races.
Just what I've been reading/watching. Makes sense to me.
Just FYI, the GT500 doesn't heat soak like the ZL1 does (by that I mean to the extent) and **** yeah 1LE!!!