There's a part of me that enjoys knowing the upper levels of a character's ability and how that might compare to another, but I think it needs to be meaningful and reliable (not 100% of the time) assessment. Not just flavor text or a way for an author to just make a character look cool. I think if it's done right, it can illustrate what cleverness can do or how limiting assessments can be. When done wrong, the author gives up keeping track, like in dragon ball, or makes a fight a guaranteed outcome.
I also think it's cool if an author has the hard numbers in their head and uses that to inform a fight on the page.
On the other hand, I also like power levels to be somewhat vague. I don't like vancian style magic because there's a set number of charges in certain abilities. I get why that works in a game for the sake of balance, but it felt weird watching How to Train Your Dragon and having dragon abilities so codified that you could count how many times it could use its breath weapon. I think I'd have been more okay if numbers like that were an average instead.
Does that make sense? What about you? Where do you stand on the transparency of power levels and rankings?
I'm not a big fan, I think they're mostly unnecessary. I really like in Jojo, how each stand has a standard array of stats that they're ranked on (speed, power, range, durability and adaptability), but its not really that important. What's more important is how you use your ability and what ability your opponent has. No matter what your power is, there's someone else out there with the perfect counter to it