That's the main difference I think. In north america, it really doesn't matter how fast your 4 door can get to 200 let alone 300kph. Grunt around town and the ability to very quickly merge onto the highway are the only two times true overwhelming power is useful on a big family sedan.
In Ontario, if I get caught doing 150kph on the highway I loose the car (regardless if there's someone else in it who can drive) for 7 days. It gets towed right there, right then. The fine is over $5,000 and insurance becomes unobtainable at worst and more than $5000 a year at the very best.
I'm not going to take a 4 door on the track, no matter how sporty. Well maybe for 3-5 laps but not regularly. So having the speed potential is more of a nuisance than a good thing. My V8 e-class wagon is more than fast enough. With super large infant seat #2 hopefully getting installed this year, we'll probably replace it with a diesel GL Mercedes so we can actually have other people in the car. Fine for power around town and more than capable of accelerating to the usual 120kph the highways travel at.
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Past-President, Porsche Club of America - Upper Canada Region