Monte Carlo is definitely a LOT brighter than Le Mans; there's a PCD thread with pics of an MCB E92 parked outside right next to an LMB E90. San Marino is basically Interlagos in hue but with the saturation cranked way, way up so it looks almost electric. Still has that "blurple" quality though.
Not to make your decision even more difficult, but for black, have you considered Azurite? Seems to be a favorite here and it has a blue undertone, which might appeal to you since you seem to like blue. Or if I were doing it again, I'd seriously consider Tanzanite Blue, which is sort of a midnight blue with this beautiful inky lighter blue undertone and turquoise flecks. There are pics of a 640i Convertible at the Geneva Auto Show as well as a 640d Gran Coupe if you search 6Post (EDIT: Thread links in a post below.) Not to say I don't like my Le Mans because I definitely do, but Tanzanite looks downright regal. It's elegant but subtly flashy in a way that makes clear that the car is something special.