[IDBGOD]

If you don't need the practicality of the 4 doors, and it looks like you are still going to have an SUV for family outings, I don't see any reason not to go for the convertible.

That said however, looks are subjective. The M3 from the rear has a much more aggressive stance than the M4 with the flared rear fenders. Front they are the same, though the rear fenders are still more pronounced at any angle. The only angle the coupe takes the M3 really is the side.

In the end you've got to decide what you like more. If you don't need the practicality of the 4 doors and don't care to have the absolute most optimum performance (kind of useless for a daily driver on public roads) I'd say enjoy some sunshine in the convertible.