You will save a LOT of money if you go for some nice aftermarket wheels. They'll be lighter too.
Save money, buy aftermarket wheels, and don't buy run flat tires.
In terms of ride comfort:
19" wheels + non-RFTs = 19" wheels + RFTs
...at least that was my case when I upgraded.
E92 335i: Space Grey|Coral Red|Aluminum Trim
Future Ride: 2015 Mustang GT Premium |Guard|401A|PP|Recaros|6MT