In M&M each character is going to be close powerwise to one another. Assuming the GM makes sure the built in limits are being used.
No, this isn't true. Last year, RJ and Tom both ran M&M games that fizzled out because PCs had wildly varying power levels - all were PL 10 but some players were more effective and efficient because they were created by players who knew the rules better.
Any point buy system with a great deal of complexity has this flaw to one level or the other.
You see, there's this topic in game design called system mastery. The term means that a player's knowledge of the game's rules gives him an inherent advantage in the game. For example, in 3E D&D, there are many feats but many of them suck ass - like toughness which gives a flat +3 hit point bonus. Compare this to weapon focus which gives a +1 to hit with a given weapon.
a person with low system mastery would probably take toughness over weapon focus since that gives a higher bonus
a person with high system mastery will take weapon focus because that +1 to hit is much more important than 3 extra HP.
System Mastery is a much bigger deal in M&M than in WT in my opinion.