Champion is more rounded to begin with but evolves into a card that performs additional roles - that being card advantage
The Avatar: The Last Airbender deal is great, but it's not the only one available right now
Collectors and many players want cards like Juzam Dijinn, Library of Alexandra and Black Lotus because of their history and significance
At the very least, at every opponent's draw step, they draw a card
EarthquakeEarthquake (40,189 Inclusions, 2% of 2,337,008 Decks) The original red boardwipe, EarthquakeEarthquake still holds up these days precisely because of commanders like Niv-Mizzet, VisionaryNiv-Mizzet, Visionary that want to be able to damage players
Your commander is what's going to get you to close out games quickly, especially since it burns all of your opponents at once as opposed to just one