I'm not implying your driving recklessley on a public road, but if you took it that way then you have yourself to blame for feeling like that. I just hate it in general (usually M3 drivers say it too) when people commend handling even though its almost never needed on public roads.
Usually when u are next to a similar powered car at the lights and u have a bit of a nice clear straight, the car that comes off looking 'better' is the one that picks up quicker in a straight line, not the one that goes round the bends at high speeds. (I know i shouldn't say this, but there is some truth in it!)
If you're talking about wet conditions etc, u will notice that nearly every merc has traction control and other necessary measure to keep its driver safe (just like the porsche must have)
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Not a good reason to buy the porsche over the merc still.