Down to the flattened -bottom of the S-Shield. Also, the consistency in thickness of the S-Shield.

In the cover on the first page of the thread, Romita's S-Shield is fat on top but thin in the sides and bottom. I wouldn't have thought it possible that an artist of his caliber would do that.

I myself favor the S-Shield where the S slightly extends beyond the boundaries of the shield so it doesn't look so much like a policeman's badge.

* Edited to add that I woke up just now to the fact that's it's drawn with some sort of marker and not a pencil.

It never looked more like the Daily Planet staff were just humoring SuperClark about his "secret" identity.

As for the "S" emblem on Romita's cover, he's clearly going for (and not getting close to) the old-style design, the one DC still employs in their licensing and animation. Lee went out of his way to "retire" that more decorative design in-story, but it is still the law of the land beyond the confines of the four-color world Lee and co. control.

Here we see Cully Hammer's model sheet for the Nu52 Superman, with its sleeker, more angular emblem. Also, an animated model with the emblem modified to more closely resemble what once was. The rounded serif at the end is still gone, but overall, the symbol is more recognizable than what Lee and co. would have. 

"I'm givin' ya 'til sundown ta git out, curlycue. There's a new serif in town, see?"

But more recently after getting JB's run of Avengers West Coast I see Wonder Man sporting that "Do". et tu Brute !