I think the main thing with powered vs unpowered is that when you randomly include a smattering of completely "next level" cards and mix them in with
Ember Hauler or whoever fills that slot these days, it creates a lot of really feel bad moments (I first picked Preordain, you first picked Ancestral Recall, that's totally fair). I think if you went all in on a powered design (i.e. designed for vintage style gameplay) it could be a fun, but would also be a completely different experience.
This really hits home with me. I know this is an idea thread for Jason, but rant incoming...
When I first discovered this format, the "power max" "best cards of all time" idea was pretty much the only thing there was. And it was novel and it made sense at the time.
Anyway, fast forward almost 10 years and I think we are at a very different place with cube. For me anyway, it quickly became clear that only running the most powerful cards was a flawed design principle for two very important reasons:
1. Over time, the power level of your meta can only go UP. That might not sound like a problem, but it's what leads to degenerate game states. Power cannot continue to increase without the game breaking down. Wizards is constantly printing a powerful set and following it up with weaker sets. Some guys might think that is by accident or because they don't know what they are doing, but it's not. They are doing it for a reason - so they can keep a constant power level over time. The only way to do that is to cycle the power of the sets they release. There is even an article about this very thing (it's a good read). In cube though, most guys aren't doing that. They are simply increasing the power of the cube. At some point (if it hasn't happened already), it will degenerate the meta. Some guys like the brokenness you see in legacy/vintage (and if this is you, then by all means live well and prosper), but for me personally I don't want to play that type of magic.
2. Running the most powerful cards of all time is not inherently balanced. And the reason for that is simple and obvious - the most powerful cards are not in and of themselves balanced and they certainly aren't balanced with each other. So running all of them with impunity by default creates an unbalanced meta and the only way to achieve any semblance of balance is to speed the meta up so you hide the degenerate nature of what you're running. There's a reason guys are pushing aggro and lower and lower CMC curves in cube. This is an oversimplification of course, but the main point is valid.
For me at least, these two two things has made the "powermax" model a non-solution. I think lowering the power level (even if just a little) offers a lot of benefits (beyond the obvious increase in design space) and I think more people will see that over time.