I mean if we're purely talking match up for starters? Gotta go with Turtwig. The whole line gets access to ground and rock TMs for coverage. Provided you get the TM, even just Turtwig can learn sandtomb and mud shot. You could do some serious damage in the first two evos with that.

By the numbers on the last Evo, Charizard is set up as a Sp. Attack sweeper but it's P. def is trashed. Torterra is set up opposite with very solid Physical Stats, low specials, lower speed and solid HP. They're pretty asymmetric. There's a world where you switch in Torterra to eat a Charizard fire attack, queue up rockslide and hold your breath that it doesn't have a special flying move in the pocket that can chew up the rest of you.

Plus, you can use it to set with stealthrock so it might not even be a bad option for leading the party given that it's beefy enough to eat a smack or two.