I'm in the camp that thinks it's just a regular SD, though I can sort of see how it might work as being the Executor.

But for those who think it's the Executor, let me ask you this: let's say it's 1980 and you've seen SW, and now you're watching ESB for the first time. You know what a SD looks like. The shot in question comes up- the massive tower fills up the screen.

It looks just like a SD tower that's been established in SW and the beginning of ESB. What about this tower would possibly lead you to believe that it's anything but a SD?

If the filmmakers wanted us to think it was a different type of ship... why would the initial reveal of it be a structure that is identical to that of a ship that has been clearly previously established in the movies?

Those in the Executor camp- do you think the filmmakers' intent was for the audience to think right away that the tower belongs to a different kind of ship, OR, after seeing the body of the Executor, was the audience then supposed to think, "oh, that first shot of the tower was actually this much larger ship"?