Corvette Gran Sport vs

I was just wondering why the Corvette Gran Sport (C7) is faster than the ZR1? The ZR1 is much further along in the game and requires a much higher rep level, has a more powerful (in theory) 3.8L V8 Hybrid than the Gran Sporr but in practice the Gran Sport annihilates the ZR1 on most tracks. Why is this? Is it worth me buying the Gran Sport and putting Elite + parts on it? This video demonstrates my point: https://www.youtube.com/watch?v=4XRqL6DQE9Q&ab_channel=ZombieHead3000