scizor w/ Fury Cutter/Iron Head

Movesets are way more important than a small difference in IVs.

A small difference in movesets is even less important. Steel is super effective against ice, rock, and fairy. There aren't really any matchups in the current meta against fairy types to be concerned with. The only ice type likely to be defending is Lapras which is a water/ice type and water's resistance to steel negates steel's/Bullet Punch's super effectiveness against ice; Fury Cutter is neutral here as well. As for rock types, you'd only have to consider Rhydon and Tyranitar. With Rhydon having ground attacks that are super effective versus steel, it's not a good target for Scizor; that leaves us Tyranitar. But bug attacks are also super effective against Tyranitar, so there is no loss here with regard to typing.

Fury Cutter may even be better against Lapras and Tyranitar: Bullet Punch has more Power/DPS, but Fury Cutter has higher EPS and less cooldown time.

And in attacks where steel is neutral, the only ones worth considering are against Exeggutor, Espeon, Umbreon, and Donphan. Fury Cutter is double super effective against Exeggutor and super effective against Espeon and Umbreon, so its typing is better in these cases than Bullet Punch's typing; with Donphan, it is a typing tie, since both are neutral versus Donphan.

So I think arguably Fury Cutter/Iron Head is a better moveset overall for Scizor than Bullet Punch/Iron Head; at the very least, Bullet Punch/Iron Head is not way more important than Fury Cutter/Iron Head as a moveset for Scizor .