Let me start by saying - Arrow - yes, I DVR and watch it every week. One of the few shows I actually watch (and not just have on in the background for noise).
As for the rest....
If the game is written with level progression as a major component (the way HARP and RM are) then gamers are forced to play in that environment and the emphasis is on progressing in powers, abilities and skills.
If the game is written with power levels as static, but having the ability to adjust them up or down when the GM says to, then the game is focused on the character themselves.
If a level 5 character is given limits to max # of DP that can be spent on a single ability, limits to their stat bonuses, and limits to their total character you end up with characters like: Falcon, Bucky, early Marvel Girl or early Iceman, and Kitty Pryde.
Level 10 characters are closer to early Colossus, Nightcrawler, Cyclops, Beast, Hawkeye, Gambit... Where they have at most one stat or ability at high levels.
Now a GM never has to consider taking his level 5 campaign and having characters (and foes) progress to 6,7, and 8 levels. The GM focuses on the plot. If later he wants Mister Metal to increase the speed of his armored flight to supersonic speeds and add more firepower he considers that such a plot development would make Mister Metal a Level 15 character. Now he knows that to avoid unbalancing the game he would need to either bring the other characters to level 15 or ensure that Mister Metal has a balanced foe to have to fight with and then introduces Magno. Magno counters Mister Metal, but unfortunately he has no ability to resist the mental assault from Psi-lass who, despite being level 5, is able to save her powerful friend. That I see as being more oriented towards comics.
The concept of different power levels remains, but the game is not about level progression so XP don't play a part. If someone wants to include them that's fine, I can put together optional rules for that, but I would discourage it as it shifts the game focus.