Michael Jackson as some sort of of supernatural undead creature, or Michael Jackson as a street-tough mediator between two rival gangs? If I was judging by which is the more fantastical, unbelievable scenario, I guess I’d go with ‘Beat It’. 
My vote for best MJ song, but I also voted with you that Triller is the winner of the two selected songs by the values the OP listed.
If I scored the same as the OP:
Vocal quality: dead heat
Musicianship: slight edge to Beat it
Lyrics: moderate edge to Thriller because, duh, Vincent Price!
Video: Thriller, and it’s not even close.
So, pretty much everyone in the thread is right, but not everyone is choosing based on all of the factors the OP mentioned, as much of the Beat it crowd are giving a (deserved) edge to Musicianship.
I think Beat It has a disappointingly flat sound to its production. My vote goes to Thriller.
I love Van Halen and love Eddie Van Halen but not seeing how his 15-second solo in a Michael Jackson song makes that song great. It’s a novelty at best. Listening to it I am not sure it really fits with the Michael Jackson aesthetic. Orange juice and milk. They are both fine but do not go well together.
Talking about Beat It vs. Thriller just reminds me of one of my favourite internet videos: the Yacht Rock episode about trying to get Michael Jackson to quit doing hard rock.
Looks like you affirmed upthread that you meant Beat It in your OP. In which case I agree. I also like the break before Eddie’s solo (the one filled with the same electronic gongs heard in the intro). And I also like Eddie’s solo.
I assume you also meant Beat It here too? I think it was less about running away from an ass-whooping and more about refusing to participate in pointless street combat. Either way, yes, still better than a song about watching a scary movie on TV.
Definitely Beat It over Thriller.
You see? No mere mortal can resist the evil of the thriller. 
I think Thriller is the better effort. It manages to take something that would be so cheesy in most peoples’ hands, a disco Halloween song, and make it work. I like how it takes the rush and excitement of horror films and equate it with his thrillin’ lovin’: “Cause I can thrill you more than any ghoul would ever dare try.”
I mean, it’s no “Werewolf Bar Mitzvah,” but it still tops Beat It.
I and my friend circle were very much into monster/horror/slasher media and Stephen King at the time, and the “Satanic Panic” was very prevalent in our hometown and schools, with teachers/clergy/counselors condemning us weird kids as being damaged and corrupt. We loved Thriller because it felt like the most popular artist in the world was legitimizing our niche to the world and reaching out to us to let us know that we were not the weird evil social outcasts that the moral majority claimed we were.
Thriller gets the sympathetic vote for me.
Agreed!
I also agree that “Beat It” is a better song, while “Thriller” is the better video… “Beat It” was probably my favorite song as a 4-yr old, and I’m listening to it now. The guitar solo is cool, but the rhythm guitar is as well.
As an aside, I always thought the bass line to “Billie Jean” came from The Doors’ “The Soft Parade”
I find “Thriller” boring. I’m definitely Team Beat-It!
The videos for both “Beat It” and "Thriller are superb, but I have to give the nod to “Thriller” for spawning a worldwide phenomenon that’s endured over time.
Also, of course, Vincent Price.
I don’t think I ever saw the video for “Thriller.” If I remember correctly, it was exclusive to MTV, which we didn’t have at the time it came out. (Those were the days of “Call your local cable company and tell them ‘I want my MTV!’”) I watched a lot of music videos on WTBS’s “Night Tracks,” including “Beat It,” and I heard the song “Thriller” on the radio, but never ran across the video. (And yes, I know nowadays I can watch it online, but I’ve never been motivated to.)
It’s pretty nice.
Overall, the video is outstanding. My only issue with it is that zombie makeup has progressed significantly in that past 40 (!) years and so it looks quite dated and cheesy. That’s the price (no pun intended) of being a groundbreaker.
If I added a new category of “Dancing” to the OP, I’d have to give the edge to Thriller as its routines are longer and more complicated than those of “Beat It”.
This.
It’s even better than Thriller when done on a single note (links to YouTube video).
That’s awesome.