Okay, welp, this is my cue.
As of right now with the TV Show, Penny completely and utterly rules in the skill department. Mark has just begun being a superhero and doesn't have too many skill-feats, like... he has not really fought much on-screen, plus, his enraged mode only has a single feat against a foe that wasn't too harmed. On Penny's side, she has fought and kept up with skilled and talented fighters like Pyrhha, Cinder, and Winter in one form or another, plus, Mark isn't anything special as he's just a basic flying brick without any notable hax.
Stamina is a toss-up, tbh. Penny has potentially limitless stamina. Lifting Strength goes to Mark. Equipment goes to Penny, which also grants her a range advantage. Will leave Penny's exact AP to the more knowledgeable folks in the Rwbyverse, but Mark's AP is 203 Tons of TNT, and his durability scales to this as well. Penny's Aura, however, makes any potential AP advantage or stat booster from being enraged null somewhat due to how it works and how it protects her.
I won't vote yet, however. I am just posting this to get this thread started.
