If your decision is not driven by need, u will not find the M5 to be more rewarding. I have both and love them both, but they focus on different things. Clearly, the M5 is more focused on luxury, space, and brute force at the expense of precision and sharpness. Not that the M5 is lacking in those area. It's just that it does the other stuffs better. If going fast in the straights while being pampered is what u are after, u will be a very happy man