"Made like a gun, goes like a bullet"
So many Enfield stories. So little time!
That is startling! Only on thorough examination do the differences start to become apparent. But the more you look, the better the "old" bike looks. A bit more curve in the C5 exhaust pipe along its run would make a tremendous improvement. Tone down the mirrors a little bit. Add the optional pillion seat (which I think looks like a double for the one on the old bike) pose the bike on its side stand in the grass, and you'd be very close.
The Royal Enfield G2 was the inspiration behind the design of the C5 and the designer S Sivakumar spent many months in England researching archival material on the G2 to get the right styling and design cues.