it's all a guessing game. When Sony and Microsoft shop companies like Intel, IBM, and AMD for chipsets, GPUs, and CPUs, these companies have roadmaps for all their products and what technology will be available when.
Microsoft and Sony know when they want to release their consoles and choose the appropriate tech that fits that timeframe. And they all have a sense of how much they want the console to cost so consoles tend to have the same prices. And this is why consoles tend to have the same tech.
It's just that there are breaking point decisions that change the fates. Like how Microsoft wanted to go with 256 GB with the 360 but Epic Games said this is what a game will look like with 256 GB and this is what a game will look like with 512 GB. And that's how the 360 ended up with 512 GB of RAM.
And remember the PS4 was going to have less RAM but it's strongly rumored that it was bumped up at a very late hour when they found out the Xbox One would have 8 GB of RAM. And Microsoft gambled that GDDR5 was going to remain cost-prohibitive and went with the safer pricing on DDR3 whereas Sony gambled that GDDR5 pricing would drop which it did. Microsoft had to factor in the cost of Kinect and that cost comes from the budget. So Sony didn't have to worry about a Kinect in their budget and used that part of the budget toward a higher end chipset from AMD (Pitcairn versus Bonaire). So you make decisions and sometimes it works out and sometimes it doesn't.
If you look at it from their perspective back then, their decisions didn't seem so bad then. Microsoft's most important markets have always been the US and UK because those markets spend the most money. The 360 dominated those markets and so they thought that they could go all in on the "One" concept. Have a device that is the center of the entertainment. They thought that all 360 customers would become One customers. Lock in. Just like with Apple. iPod owners because iPhone owners. And iPhone owners almost always remain iPhone owners.
But the thing with Apple is their customer base is different. They are not stat heavy. iPhone never had the best hardware. But they had great hardware with a great software ecosystem. Gamers are macho. It's hard for them to accept a machine viewed as inferior. They spent hundreds of dollars on consoles and games and want to feel vindicated that they made the best purchase. And they need to convince their friends what the best purchase is and then it becomes a mob mentality.