Both of them are based on the same AMD Jaguar architecture, with relatively minor differences between them overall, and any developer or publisher claiming they're "not used" to this kind of architecture is lying through their teeth; it's standard x86-based stuff, and virtually every programmer on the planet knows their way around that. The main benefits are that the GPU and CPU are on the same chip, and the overall architecture being oriented toward low cost, low power consumption, and low heat. Whether the games being developed are natively 64-bit is anyone's guess, but both systems are capable of it.
That said, the XBox One has some deliberate, inborn deficiencies that were implemented in order to lower the cost of the console, since the inclusion of stuff like Kinect drives the price a bit higher than the PS4 as it is, and matching it spec-for-spec would push the cost up into a less marketable range than it's already sitting. They've already gone on record with stating, in PR speak, that some games will be running at lower resolution - the spin being that this is a benefit that will allow for better performance. It's technically true, but overlooks all the associated negatives, and is hugely misleading to people who don't understand how all this works.
Shorter version: They took low cost hardware, made it even cheaper by stripping some shit out in order to justify the cost of a big camera, and tried to excuse it by claiming that running games at a sub-HD resolution that isn't the native resolution of any modern HDTV is somehow a competitive advantage.
