I don't know about the coating - although I had an old-type 50/4 for a while years ago, I've never had the opportunity to do a direct comparison of old and new types.
Re barrel cosmetics, easiest just to point to some photos.
Scroll down on this page for a picture of the N-type 50/2.8:
Scroll down on this page for a picture of the old-style 50/4:
The picture on this page is the A-type 150/5.6 - possibly a mismatch to what's actually being offered:
A lineup of older macro, micro and EL lenses, with an N-type EL at the far right: