The signal receiving (from the probot) is nearly identical.
However, if Vympel is right, this is overriden by the movie.The annotated screenplays on page 141 wrote:Darth Vader's Star Destroyer, larger and more awesome than the five Imperial Star Destroyers that surround it, sits in the vastness of space. The six huge ships are surrounded by a convoy of smaller spacecraft. TIE fighters dart to and fro.
The arrival is different. The draft talks about six star destroyers resting, the novelisation about six IMPERIAL star destroyers resting and the screenplay about six star destroyers moving.
Prior to Piett reporting that the MF entered an asteroid field:
Draft/novelisation: Vader's Star Destroyer + two others, flanked by several smaller Imperial warships.
Screenplay: No number specified.
Asteroid collision scene:
Draft "One of the smaller Imperial vessels in the foreground gets hit by a huge asteroid and explodes."
Novelisation: The same, except that from Vader's POV.
Screenplay: The hit is completely left out.
Movie: An asteroid collides into the left side of the tower of an ISD, after the impact part of the tower becomes invisible, but at least the rear 'neck' is still visible.
Hologram scene:
Draft/novelisation: "Before him are the hologram images of twenty Battleship Commanders. One of these images, the Commander of the ship just exploded, is fading quickly away at this moment. Another image, in the center and a little apart from the others, is faded and continually disrupted by static." The novelisation is slightly confusing (not the only case, try to count how many times the Avenger is destroyed ...), when the reporting is over, it still talks about twenty holograms. In the screenplay, no number is specified.
I think there are many interpretations.The annotated screenplays on page 172 wrote:Before darth vader are the hologram images of battleship commanders. One of these images, the commander of a ship that has just exploded, is fading quickly away.
The bombing scene is again quite different:
Draft: "Looking down on two medium-sized Imperial cruisers moving across the surface, dropping bombs which create powerful shock waves centered around blue explosions."
Novelisation: No size specified.
Screenplay: The scene is nearly absent.
So, the exact size is unknown. The most frequently used figure is the Executor plus five ISDs (plus many smaller ships), however, as the fleet raced toward Hoth, there may be ships that could only join later, so it can be used as a lower limit. The upper limit can be gained from the twenty holograms of "battleship commanders", however, it is unclear what ship that could mean. It is referenced as a "smaller" ship, but since the Executor was present, it does not mean a lot. Also, it does not help that Needa (captain of an ISD) was one of them as the novelisation later talks about Needa plus nineteen others and the collision in the movie clearly not destroyed the ISD. So, they can be larger than ISD ships those joined the fleet after the Battle of Hoth, as well as ISDs or even smaller ships ...The annotated screenplays on page 177 wrote:EXT. SPACE-STAR DESTROYERS- ASTEROID FIELD
The Imperial fleet around vader's ship is surrounded by the asteroid storm. Smaller Imperial vessels search for their prey.
EDIT: BTW, the Executor plus five ISDs were described in the novelisation (the probot report receiving scene) as being more terrifying and to have more destructive power than anything in the galaxy ... Personally, I think it fits quite well to the six ISDs as the core force against industrialized worlds figure in the ICS.
