You both are reading the generation 7 wrong. PS3 flopped because it was too powerful. That is the main reason. Power is a disadvantage because it goes hand in hand with a higher price. XBox360 and PS3 had mostly the same games, but XBox360 was cheaper. That made it the dominant platform in the US and UK.
The worst thing Sony can do is make PS5 more powerful than Scarlett, because that will drive up the price. Even if it costs $50 more, it will be a repeat of generation 7. Given it won't help Microsoft in non-English speaking countries, but the US and UK are ready to go for Microsoft again if given a decent reason like a cheaper price.
Not true; PS3 really wasn't that much more powerful than the 360, it was even weaker in some ways. It was expensive cos it used a ridiculous over-engineered custom chipset and a Blu-Ray player.
PS4 was cheaper than the Xbone yet it was more powerful. PS5 could exceed Scarlet's power at the same price launching a year later.
PS3 was more powerful than the 360. I am including the Blu-Ray drive in that, since a Blu-Ray disc has significantly more capacity than a XB360 disc. Overall the specs on the PS3 were clearly better (disc drive, clock speed, hard drive, etc...), but that drove up the price.
PS4 also proves my point, because the PS4 launched at a cheaper price and it trounced on the XB1. Price matters a lot. Price matters so much that it also makes power a disadvantage. All other things being equal the weaker console has an advantage over a more powerful one. Of course an expensive peripheral like Kinect can totally destroy that advantage, but that doesn't change the fact that having the weaker console is an advantage. This is especially true when comparing Sony and Microsoft consoles, because they get mostly the same games. In the end a lot of people just buy the cheaper console, and the easiest way to be cheaper is to be weaker.