>>538066914
I'd say Knuckles because he's more prone to comedy relief, but he still gets the occasional bone.
Sega just stopped using Metal as Eggman's right hand and nowadays he gets a standout boss fight at best. Rivals 2 did have that one mildly interesting bit where he pulls out the Chaos Emerald powering him so that Shadow can escape the Ifrit's dimension and Sonic 4 episode 2 tried to make him a secondary antagonist like in CD and Chaotix, but until Sega actually Metal to win in some fashion, nothing's liable to change.