I was saying that Magneton outclasses Magnezone as a scarfer because of its superior speed tier, but zone outclasses it in the air balloon and specs sets.
Scarf Magneton does not outclass Magnezone, because besides checking birds and trapping steels, Magnezone also serves as a Fairy check, which Magneton can't really do due to its lesser bulk preventing it from switching into Fairy type attacks, as well as other stuff like Latis and Kyurem-B. Just to give you an idea :
252+ SpA Pixilate Mega Gardevoir Hyper Voice vs. 0 HP / 0 SpD Magnezone: 137-162 (48.7 - 57.6%) -- 94.9% chance to 2HKO
232 SpA Pixilate Mega Gardevoir Hyper Voice vs. 0 HP / 0 SpD Magneton: 151-178 (62.6 - 73.8%) -- guaranteed 2HKO
252+ Atk Choice Band Huge Power Azumarill Waterfall vs. 0 HP / 0 Def Magnezone: 211-250 (75 - 88.9%) -- guaranteed 2HKO
252+ Atk Choice Band Huge Power Azumarill Waterfall vs. 0 HP / 0 Def Magneton: 249-294 (103.3 - 121.9%) -- guaranteed OHKO
252 SpA Life Orb Latios Draco Meteor vs. 0 HP / 0 SpD Magnezone: 151-178 (53.7 - 63.3%) -- guaranteed 2HKO
252 SpA Life Orb Latios Draco Meteor vs. 0 HP / 0 SpD Magneton: 185-218 (76.7 - 90.4%) -- guaranteed 2HKO
252 SpA Life Orb Latios Hidden Power Fire vs. 0 HP / 0 SpD Magnezone: 187-221 (66.5 - 78.6%) -- guaranteed 2HKO after Stealth Rock
252 SpA Life Orb Latios Hidden Power Fire vs. 0 HP / 0 SpD Magneton: 229-270 (95 - 112%) -- guaranteed OHKO after Stealth Rock
As you can see that's a pretty significant difference in damage, and definitely makes Magnezone worth running over Magneton as a scarfer.