You're seriously comparing a BRZ to a Cayman.... There are soooooooo many variables there, I don't even know where to start. Chassis stiffness, quality of suspension, tire, front engine vs mid engine, overall build quality and chassis tuning. My God, you might as well compare a Chevy Volt to a Honda Civic Type R. Anyway, back on topic, I don't think the balance between the I4 and I6 will matter much. IF there is any improvement at all, it'll be negated by the power difference.