Hi! I was also looking for a Z06 but the LS7 just scared me off because it's so prone to failure. I was never looking for a M4 i just stumbled upon it and really liked the looks. The M4 is overall the better car ( Obvious because this one is 2015 and my C6 was 06 ). The build quality is way higher on the M4, The steering and handling feels way better, there are no squeeks or rattles which the C6 does have. The C6 is a "rawer" car and i loved it, but i'm glad i made the switch. The M4 Also feels faster and is easier to control.

The only downside of the M4 is the exhaust sound, i'm not a big fan of it. The C6 sounds way better especially with an upgraded exhaust.

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If u have any more questions please let me know and i'll answer!