What Would Take Over The World Faster: The Thing (John Carpenter) or a pack of Xenomorphs?

Not really a battle, gonna move to off topic.

And the Thing

The Thing for sure. It's not even comparable.

the thing

Wouldn't a queen need to be dropped in for the Xenomorphs to actually spread?

Probably The Thing since it can blend in so well with humanity. Xenomorphs can reliably be killed by normal humans with conventional firearms, so there's a decent chance that a small pack of them would be killed off before they can really do anything.

Male Xeno's can make eggs if completely isolated and with no other options. This apparently happened in the first Alien movie as the male there seemed to be converting the crew to eggs.

That being said, People would run from the Xenomorphs and would be on high alert, while the Thing can effortlessly blend in with normal people and is nearly undetectable. Given that it would also breed like mad, it would be a while before anyone figured out what was going on, and it would be too late by the time any major group noticed.