As already mentioned, the final cutscene is based on whose morale is highest (Hawk or Panther). It's actually quite a bit more complex than any one decision. There are three major decisions between the two, which either give +1 Panther/-1 Hawk or +1 Hawk/-1Panther:
Hawk and Panther are arguing on the bridge: "There's always hope" vs. "We die trying"
Speradon or Circe: "Panther's right" vs. "Hawk's right."
Bypass or destroy Ella: "Panther's right, we can't kill civilians" vs. "Hawk's right, this is war"
Each character also has two conversations where you can effect *only* their morale:
Panther-
Panther at the bar: "She's dreaming" / "You'd think..."
Catscratch and Panther talking about fighting the Kilrathi: "Straighten this kid out" / "Do I look like I have all the answers?"
Hawk-
Did you enjoy fighting the Kilrathi?: "Gotta admit, I did" / "This guy is bloodthirsty"
Argument about the Kilrathi: "He's missing the point" / "Bitter guy"
... then, depending on which system you go to (Circe or Speradon), you get a second point to add or remove from the person you supported. These effect only the person you previously sided with (so they can either negate or double the number of points added to your choice).
Talk to Maniac or let Panther hurt him? "Maniac's on his own" / "Tempting, but I can't let that happen"
Talk to Maniac or let Hawk hurt him? "What a whiner" / "Time to be a captain"
... so, it's possible to attack Ella and go to Speradon, as long as you lower Hawk's morale at several other points to make up for it (and raise Panther's).