I have always coveted an E86 M roadster. I
really like that body style in the hardtop configuration. If you are at all mechanically inclined, I'd think restoring/modding an M Roadster would be as much fun as driving it. To me, those cars have a timeless aspect that the E89 may not have. Plus, the N/A motor should have more longevity than the turbo'd car.
As much as I love our E89, I might have to go E86 M if I had the opportunity.