between the 2, I think the IWI is worth the extra coin. I owned a RFB some time ago and could never get it to run right, regardless of ammo & gas setting. I sold it at a loss and haven't looked back. I couldn't even get high quality ammo like FGM 168s to consistently cycle without opening the gas so much that it was abusing the brass. I love the innovation and value that Keltec brings to the market, but I just won't own unreliable carbines.
I've owned an X95 and thought it was great, though I sold that too. As much as I liked the X95 I still preferred my Aug A3.