Full Bug Scizor vs Full Metal Scizor in the current meta

Bug is better.

Bug for Alakazam and upcoming level 5 raids.

But covers grass, dark, psychic
- unfortunately, many grass types are dual grass/poison and receive neutral from bug. As well I don't see many grass types in gyms
- hits exeggutor super hard and will hit Shiftry hard in gen3
- every generation has psychic legendaries
- covers Tyranitar and popular psychic types (many)

Steel covers rock, ice, fairy
- unfortunately, many ice types are dual water/ice and receive neutral damage
- in situations where rock types exist, they are either ground/rock or water/rock, in which grass would be more effective
- there are few relevant fairy types, if any

BP/XS Scizor 15h 14a 13d Worth a fast TM?

Bug, FC has awesome speed and loads the power bar almost twice as fast as BP. And as EruptHonorFace described, psychic legendaries in every generation, Tyranitar and Exeggutor are covered by bug as well.

I have one of each Bug/Bug and Steel/Steel. I have two with Night Slash (so in a few months once I take care of other priorities) I'll change the Night Slash and make the fast match (hopefully without TM).

I also have 2 double bug scythers and Pinsirs to get me by for now.