The thing with MGXHYUButo (bad name, now shortened to HMButo) is that it beats nearly ALL leads.
Meowth: Surf, AJ, FO Resist blah blah
Snover: If scarfed, both die as you hang on with your sash as they hit you while you OHKO with Rock SLide, and then hail kills you. If not scarfed, then RS is an OHKO unless extremely bulky. If SUbSeeder, just lay SR, break the Sub, get the fuck out.
Phanpy: Surf 100% OHKO, even for 36 SDef versions. Then you still have your sash and can set up SR, unlless Phanpy uses Ice Shard turn one (which is p dumb)
Houndour: hard. However Kabuto outspeeds LeadDour who only has 14 Speed, and KOs with Surf + AJet.
ehhhhh what elseeee
Machop: Dunno
Riolu: KOd by Surf + AJ, not sure if outspeeds
Dratini: Rock Slide x2
etc other anti leads are p uncommon, and Im sure one can just go for the SR -> AJet on them.
But against the main leads, its not guaranteed to get SR up, but most definately likely to come out on top. This way although you arent getting SR up, you are certainly stopping either their SR or if anti-lead a vital member, as Anti Leads are often used to get momentum going, which you have snatched them of.
Hence I support HMButo as our lead.