I don't think, under the vast majority of real-world conditions, you'll see any difference at all between CF and CFi lenses. As the poster above said, the only real change optically was maybe a bit better flocking to prevent stray light scattering, which *might*, every now and then, result in slightly less flare or minutely higher contrast under exactly the right conditions. There should be no difference whatsoever in the optical formula or the glass composition/coating.
I have both CF lenses (four of them) and CFi lenses (two), and I can't see any real differences in the quality of the images from the two types. I do rather like the ergonomics of the CFi lenses just a tiny bit more. But really, it's not at all a big thing, and I use both kinds interchangeably during shoots and don't, when switching from CFi to CF notice any annoying degradation in ergonomics. I really don't even at all notice the differences between the two in the heat of a shoot.