i ordered 18. i think dark colored rims look good with melbourn red (color i ordered). dark rim on silver is not bad either.
also, i will probably opt for aftermaket wheels at some point, so really no need to pay extra for the 19s. yes they will have better resale value, but i would rather save the money for now.
also i believe there is a delay in production for cars with 19s.
E92 M3 DCT