There was a little known third option. Drawings were prepared of the Burlington E-5s with the classic Zephyr shovelnose. I don't know how seriously it was considered. The drawing was reproduced on a website perporting to show the "Siiver Charger" from the General Pershing Zephyr, but the two 12-567s tended to give away the mistake.
While the slanting nose was elegant, the actual geometry of the nose was the same in each version. One reason the nose looks so good is that it is a solid of revolution of a shape made up of two radii, large in the centre and small at the sides.
So a section through the vertical portion of the nose and the horizontal portion, normal to the surface, is the same. The guys in GM styling did a really good job in 1937.....
So for the FT, the section was just rotated a few more degrees to give the steeper nose. Of course, the theeoretical shape was converted into steel dies in a press and the dies didn't have to change between the two nose angles.
The adoption of the steeper nose by the E7 gave more space for equipment in the engine room.
A much more significant change is represented by the E8. About the only thing in common with the earlier locomotives was that they had two 12 cylinder engines.Even the engines were arranged differently in the body.
The only people who ever rebuilt a 201A powered E unit to 567 power were Southern Pacific, who rebuilt their E2A from the 1937 City of San Francisco into a slightly odd E7. EMD kept the trucks, motors and generators from their trade-ins and built new E8s around them.
Incidentally, the reason that E9s were more powerful than E8s was because they had bigger generators, the D15 in the E8 being limited to 1125 HP.
The old EMDs looked nice but were maintenance intensive with mechanical fan drives and more complex radiator arrangements. UP even rebuilt every last E7 as an E9, and not because they wanted a consistent looking fleet.
If I had to run a service, give me an E9 in preference every time.
Peter