The advantage you get from turbos at altitude is identical to the advantage you get running a blower. The higher the pressure ratios, the bigger the advantage. I.e., 1atm of boost on a turbo vehicle vs 1atm of boost on a supercharged vehicle will see the same power reduction at the same altitude. At 1atm of boost you’re running at a 2atm MAP, while a n/a motor would be running at 1atm. If ambient pressure is 50% sea level for example, the n/a vehicle would lose 50% power, while the boosted vehicle would only lose 25% since it would still be at 1.5atm MAP, turbo or supercharger doesn’t matter.
The 3.5 has an advantage because the factory boost levels are about 6-7 psi higher than the predator.