Personally, I think the Excalibur was MUCH more a superweapon than the terror star. More hit points than I can count, armor thicker than my skull, and speed which would rival me running from those high school bullies.
Terror stars were just there to wipe out planets that weren't worth taking in my opinion (though I love them just the same). By the time you destroyed all of an enemy empire's planets, you could have taken them over dozens of times over with less fuss.
