XC-W/XCF-W is, as far as I know, an American anomaly. Over there some states have some strict rules about what can be street legal so to make it simple KTM have built the EXC to comply with all-state legislation. Consequently the EXC has all the road legal stuff like turn signal indicators and anti pollution gizmos. Not much (if any different) from our EXC as it leaves the factory but, as VW have discovered, you can't go claiming one thing and be operating something totally different. Over here every EXC has all the anti pollution and restriction gubbins removed at PDI
The XCF-W range is a post-PDI EU spec EXC without the lights and associated road legal wiring loom. Engine, gearbox, chassis, suspension is all EXC - just no lights, speedometer, horn and lighting loom.
The XC-F is a closed course bike, never intended to be street legal and more suited to faster cross country (XC) riding. Consequently they start with the SX-F engine, frame and suspension and add a few bits to make it suitable for cross country stuff (18" wheel, side stand, wide(r) ratio gearbox). The XCF is really just a converted motocross bike.
Pre 2011 it wasn't as clear but the general idea was there.