Conventional wisdom in RPGs dictates that all the members in the party of players should be equal. Not necessarily the same, but that all their powers, items, abilities, attributes and experience should even out. Plug every thing about the character into some magical formula and you'll get a measure of how good they are. Experience points, level, karma, the names for such things are many and varied, and all but the most beginning player knows that that's not the whole of the story. Every one who games regularly develops their own formulas for evaluating what makes their character good. You use that formula to decide to take one skill instead of another, skip developing a particular power in favor of others, choose a level of one class that gives you the most benefit.
But why? What is it about RPGs that demands our characters all be equal, or at least 'near enough'? Looking at conventional fantasy and speculative fiction, it's actually quite rare for all the members of a story to be of the same power level, even just looking at the characters who could be considered PCs. Bilbo Baggins is definitely not equal to Gandalf the Grey. Yet, for all that, Bilbo is just as important as, or more so than, Gandalf throughout the entire story.