If you vibe with Penn – if it is your favorite – and you are certain it’s affordable, go ahead and apply ED.
You can try to estimate your chances based on how your stats compare to past classes, but we’re missing one huge piece: we don’t know what any school is looking for exactly. We know that most try to fill a diverse class, with a plethora of different interests, but we don’t know how exactly you fit into that puzzle. Or, better put, we don’t know which schools’ puzzles you fit into.
So when you look at a school with <10% admit rate, it is safest to assume it is a reach for you. That will decrease disappointment if you don’t get in, and heighten the party if you do.
I think you stand as good a chance at Penn as most other applicants, and ED will very likely increase your chances… but I would never tell you to expect to get into UPenn. UPenn is nobody’s safety or even likely… barring athletes and development cases.
That being said, the only way to have no chance is to not apply. So swing for the fences. Just remember to have a safety you wouldn’t mind attending in your back pocket.