Cbars are great goggles if you really want to customize them. I/O's are great if you like a lower profile goggle that you can change goggles on the fly.
Ive used both goggles and I personally like the I/O's better. I think they look dope as hell, I never have fog issue's and the lens changing system works great.
All in all i was completely satisfied with my purchase.
That being said yes you can still change a crowbar lens fast if you get used to it...but I still prefer the I/O's
I have Crowbars with the Pink Iridium Lens, this is excellent for any day, sun, overcast, and even night. This depends more on the lens than the goggle, so I/O vs Crowbar wont make a difference here. All Oakley lenses are interchangable, even when not advertised.
I almost bought the I/Os until putting them on back to back with the Oakleys and realizing how much better the triple layer foam on the Oakleys is. The I/Os and Crowbars are both really expensive, but with the Crowbars you are getting what you pay for. Crowbars have better foam that seals nice and tight, the outriggers are a must for comfort over the helmet, and that Pink Iridium lens is the best I've ever owned.