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.
Past:'08 E92 335i|ZPP|ZSP|6AT|four (4) HPFPs
Present:'15 Mustang GT|401A|PP|6MT|Recaros
Sig pic unrelated. I like to go sideways and stuff.