Steelix or Scisor?

I think Scizzor has the better movesets for mon you would see in a gym: T-rex, Espeon, and most of all he would be super duper effective against Eggman. GP doesn’t think he’s a good defender, and I have no experience with him at all so I can only comment on his stats/moves.

Scizor

Both of these pokemon arent' super optimal. Scizor is a great attacker into almost everything but his HP is pretty low and movesets can be dissapointing (I was lucky to get FC/Xsc though)
Steelix, on the other hand is a good defender with good typing but he doesn't have very high CP
I guess you should go with Pokemon you like more.

Evolving Steelix is less stressful. Good defender no matter what moveset you get. It's great seeing one in a gym. His defense stat is crazy, making his HP much larger than it actually is. He can also pass for an attacker if you get dragon tail.

Scizor is definitely more useful. Neither pokemon are great defenders (Steelix is very good, but his CP is tragically low), and Scizor has the better attack movesets. Currently the best steel attacker in the gym meta, and he's a pretty good generalist attacker w/ either double-steel or double-bug movesets. He's also pretty decent with Fury Cutter + Iron Head because of the quick energy generation of FC, you'll basically be firing off charge moves constantly.