Medicham doesn't even need CC to kick ass. Rockslide and Hi Jump Kick don't exactly hold Medicham back.
Scarfcham is amazing (especially as lead), but Medicham can actually pull off other sets well. It's the game's scariest Choice Bander, with the unique ability to 2HKO Cresselia with Double-Edge. It gets Baton Pass to "keep chains alive"; in BP teams an Agility passed to a Life Orb Cham is quite good, especially since you can keep Passing around.
Also, Gallade's too slow to sweep, has to Egg for Will-o-wisp, has decent but not quite good enough Defenses, and less attack and speed than Medicham. It's basically the "jack of all trades, master of none" everyone's been talking about. But I have to agree, Gallade is a much cooler wallkiller than MixApe.
I'd rather be a jack of all trades, than only have one, a very predictable one at that.
Medicham dies when it uses DE on Cressy. Plus, Gallade and cham have the same speed, so if Gallade is to slow to slow to sweep, so is cham. If HJK misses, cham is screwed, as it takes a lot of recoil, like using DE against Cressy. Also, Gallade has SD and Night Slash, allowing him to defeat Cress without killing itself.
The one thing Cham has over Gallade is higher attack. Gallade has the better movepool and better stats.
What's the problem with WoW being an egg move? Psycho Cut is an egg move on Cham. Egg moves don't hold a poke back. o_O