I have a 540/6 and have never driven an M5. I can't even conceptualize in theory why the 540 would be better suited as an everyday car compared to the M5. Could it be the 17" wheels not as prone to bending in potholes? The spare tire? Better gas mileage? I don't see why the 540 would beat out the M5 as an everyday driver. Heck, if I could afford it, an M5 would be in my driveway right now, and I don't think I'd be giving anything up. Can anyone shed some light on this topic?