I had a pair of Curry 9s and have the Flotros. The fit as far as the footbed is similar with forefoot width and length pretty much the same. The 9's are a bit tighter in the mid foot (i'm a wide footer btw) but not problematic.
The upper is the major diff. The knit on the flotros hug your foot top to bottom since the vamp is all elasticized and sock-like. The 9's have a traditional tongue and warpknit which is flexible but sort fit like a normal mesh, not elastic at all. So doesn't consistently hug your foot at all times, but they tighten better than the 9's because of the traditional tongue. The 9's have more vertical space over the toes while the Flotros sort of taper down like the original 4's. Of course, since one is a low, the other is a mid-high, the ankle feel is totally different, but both extremely comfy, esp for wide footers like me. Hope that helps.