My opinion would be both. The worst part is trying to decide which one to drive today. The GT is a real pleasure to drive but becomes boring. The ZL1 is just flat out an animal that is one of the most engaging cars on the market. I will say my ZL1 is holding what I paid for it and the GT is...
Sure thing. VIN is 1FA6P8CF2R5402984.
It's nothing you really hear. It's more a feel in the 'seat of your pants" And it isn't really a vibration either. I've had '18 GT, 18 GT350 and 20 GT500 so I'm pretty familiar with the feel of the car.
I am getting a weird "rumbeling" noise in mid-gears on highway mostly. I thought at first tires but it's more like driveline noise. 6 speed GT. Exhaust on or off.
The biggest issue I have seen talked about is where they final snap the bumper covers on and chip the paint on the corners. Mine, fortunately, is perfect.
I just gave mine a really good detail Saturday and checked everything over again. My gaps are perfect and my paint looks great! I feel bad for the OP but I believe he is the exception, not the rule.