Well if you don't really feel like breeding then Swords Dance is fine, but even if Chomp is faster by two points with a Scarf, the fact that Charizard also gets an attack boost and the ability to switch between attacks makes up for it. With Stealth Rocks damage, Charizard will find itself being easily revenge killed by faster threats such as Keldeo and Terrakion, Chomp, Mence, Lati@s, Starmie, and so on. With Dragon Dance, you outspeed these threats assuming they're not scarfed. It has so much more sweeping potential, and a Pokemon that's used to put pressure on opposing teams, will find itself switching a lot, which Charizard does not want to do since it has a heavy SR weakness.