Like you're forgetting we're talking M&M not D&D, AC/Defense isn't the only number to deal with. An opponent could have shifted his PL caps favoring Toughness over Defense creating a binary yes or no between the +5/+15 Attack and +15/+5 damage examples that you think are exactly the same thing when clearly they are not, it's like saying Rock Paper Scissors Lizards Spock are all the same thing. Oh, and even the game designer disagrees with you in his official FAQ that All Out Attack and such ignore PL caps.
[sigh] ... a 10% chance at $100 and a 100% chance at $10 have the same expected value.
This is the case with attack and damage trade-offs. That's why PL caps exist, that's how they keep things balanced. That's like their whole point. Likewise, defense and toughness are also PL capped. If Batman gets hit, he gets hit hard, but his defenses are such that he doesn't get hit all that often. The Hulk is the opposite. But, their aggregate numbers (meaning the joint probabilities) are the same.
Your citation to Steve Kenson is (1) an edition out of date, (2) borderline incoherent. All-Out Attack is of course sensitive to PL-Caps, it's just shifting from Defense to Attack. The aggregate of all your PL capped things are still the same (4 x PL). Oh, and the citation you listed doesn't even refer to All Out Attack, so ... ummm, yeah. It refers to Sneak Attack, which was explicitly PL-capped in 2E and no longer exists in 3E. The defense maneuver does allow you to have a higher defense b/c you're spending your entire round doing nothing else.
And, Steve does not have much of a reputation as a rules guru ... he's very much an eyeball it kind of guy.
All-Out Attack does/did cause a but of a furor among M&M players b/c you could alpha strike your enemies and take them out before they could respond, thereby negating the disadvantage of All-Out Attack, to wit, your terrible defense. This was more of an issue in 2E M&M b/c of the way stunning worked, which is a significant improvement in my opinion with the new edition.
On the same token.
a. Find me a optimized my Cleric thread that doesn't suggest DMM(persist), points it's its about melee and no Ordained Champion.
b. Find me something that doesn't agree Mc Wizard can do everything better than Mc Fighter can.
D&D has more sameness within it's design than you seem to think it does. D&D has a sort of spoiler effect, the less useful it is directly relates to how little it will ever get used and it ultimately encourages a one class to rule them all ideal which M&M's literal core concept is about preventing.
The reason characters are seem different in D&D is because you choose to flaw your character out with no benefits (eg I'm going to play a monk!). Where as the reason characters are different in M&M is because the system encourages you to be, as you have an equal potential to be as powerful as you wish to be as either a swashbuckling pirate or spellcasting wizard. Be who you want to be and excel and what you want to do as you want to do, total absolute freedom without sacrifice. Which is exactly 180 degrees from your current view point.
I agree with the bolded statement.
The rest -- that all clerics have DMM(persist) and so on -- I vehemently disagree with. Furthermore, I cited actual examples in my post, which you blithely ignore, of two totally optimized characters (arguably too optimized) who have radical differences in their mechanics and numbers.
In M&M, that will simply not be the case. You will not see a character who had radically more defenses than another b/c their aggregate "defensiveness" will all total out to PL x 2. That's intentional. So, yeah, you're right that your M&M pirate and wizard will be on the level playing field. But if "excel" means "better at it than the other guy" then no, you're wrong. Their aggregate combat numbers will be, in aggregate, the same. That's the whole point of PL caps. There's a good thing (as noted) and a bad thing to that.
Frankly, I don't know how that's even contentious. It's like among the most obvious things from playing M&M. There are exceptions to it, namely the exceptions to the PL caps, but they are (1) very few, you can probably count the on one hand, and (2) a cause of wariness.
P.S.: I say this as someone with deep affection for M&M (even though I have some annoyances with the 3rd edition) and who runs and plays it pretty regularly. It's a great system, and the best one for superhero, and probably for many other genres (e.g., many anime-inspired ones).