I was wrong. Looks like you can get a flexible cutter bar on the HD 50F. So you get the hinge header but with a true flexible cutterbar. So basically what JD is calling their rigid cutterbar hinged frame header (HD 50R) Macdon calls their flex header. So who is behind how now??
IMO The HD50F is the best of both worlds. Flexible cutterbar with a hinged draper. Whereas the MacDon doesn't have a flexible cutterbar. It's a 3 section ridged head.