180's vs. 190's

[cbirk]

Okay, been doing some research on running a 180/55 on the back of the R1 vs. the 190/50 it comes with stock. I'm thinking about it from a financial aspect AND I read the 180 makes it more nimble, yet theoretically wouldn't that mean less contact patch?  (also heard they come with that size for reason )  Anyone here running a liter bike (or equivalent tire size)  have any experience with this? pros? cons?   Any advice would be appreciated very much thanks.