I'm too busy/tired to write a full analysis, so I'll just be nice and sweet.
Layout/Legality: Halberd wins this, because it's open, and never cramped, and the hazards are light enough that they'll barely do anything to you. Luigi's mansion is just too crazy for the ceiling techs and the lost power from hitting the mansion, instead of a player.
Artistic Value: Halberd wins again. Luigi's Mansion is a pretty nice sight, but that just can't compare to the awesome sight of the Battleship itself. Such beauty, such regality. Wow.
Music: Again, Halberd wins. Honestly, Halberd is one of the Top 3 or 4 stages for best music. Incredible selection indeed. Every track fits the stage in some sort of way, even the Forest/Nature Area from The Amazing Mirror, a GBA game (good game imo). Luigi's Mansion has some dark music that fits with the stage, but overall, it's quite dull compared to Halberd's music.
Fun Factor:
Again, Halberd wins. While flying around, being able to utilize the stage's one-sided solidity can cause confusion in some opponents, and just gives you more room to play in general. Luigi's Mansion is just so limited because of the mansion. If the mansion is broken down, it's an ok neutral stage for a bit, but then the crappy old mansion returns. Oh ya, those hazards at Halberd are so slow, you can't do anything with them, unless your opponent is really bad with DI.
Halberd wins, 65:35.
Lol, that's a shortened version, and it's still longer than anything I see on this thread. XD