I won't know about that...
When it comes to older vs newer consoles, there isn't really performance increases in terms of processing power, gaming performance, graphics, etc.
What really is happening is that manufacturers (Sony and Microsoft) continues to improve their console's hardware by using more efficient components, better cooling, improved circuit layouts, etc (even if it is just minor improvements). This result in the newer consoles that tend to be more energy efficient, running cooler & quieter, last longer, maybe weigh a bit lesser, maybe even some cosmetic changes, etc.
The only "performance gain" I've heard about is that a game may load a little bit faster on a newer console compared to the loading times on that of an older console, but I have yet to see that for myself.