No, it is unequivocally true. The Durango memory topography is more complex, fullstop. When you compare otherwise very similar architectures where one has a single highspeed memory bus, and the other has two memory buses where the majority of the bandwidth is concentrated in a very small amount of memory, the second will be harder to use effectively. It is not even debatable, and that's before you add in all the specialized hardware intended to alleviate the limitations: DMEs with built in compression hardware. On Durango you have all these different buses, and units, and data formats to juggle in hopes that you get your data where it needs to be in time, and all that moving stuff around and preloading, and decompressing on the fly, all that consumes bandwidth as well. And all of that is completely unnecessary on the PS4.
60% of Durango's overall memory bandwidth is allocated inside 32MB of ESRAM.
Around 92% of the Xbox 360's overall memory bandwidth is allocated inside 10MB of EDRAM.
I've just shown with this that the Xbox 360 is an even more egregious offender on the very terms that you yourself just set. Why would Durango's memory bandwidth setup be any more difficult to manage for developers than the Xbox 360's was if this is the case?
The PS4 will have to move data to and from system memory, just like the new Xbox will have to. Moving stuff around, as you put it, will also very much be necessary on the PS4, as will preloading and decompressing on the fly, which will also consume bandwidth on the PS4. The PS4 isn't somehow magically immune from having to do these things. The PS4 will just do so in more traditional ways, presumably, of course, without using fixed function hardware such as Durango's Move Engines. Durango isn't somehow forced to use the move engines at all times and can move data around in the same traditional ways that the PS4 can. Microsoft's own people basically attest to this very fact in their predicted typical usage scenario for Durango, where the move engines are idle and consuming none of the bandwidth. The PS4 will utilize shaders to move data around, which will, in turn, consume bandwidth every bit as much as it would on Durango. The important thing about Durango's move engines is that they are able to operate simultaneously with GPU computation. In compute heavy situations, Move Engine operations essentially come for free because the available bandwidth will be there to supply them to do their job without necessarily taking away from needed bandwidth elsewhere. The more interesting thing about them, and is a situation in which the memory setup of Durango becomes very convenient, is that even in bandwidth heavy situations, the move engines may still have plenty enough free bandwidth to do their work effectively free if the move engine is using a different memory pathway from the pathway being used by a shader.
The move engines aren't something that I see as a disadvantage. They only help and can be perfectly idle if the develop doesn't need them for anything. Developers don't have to use the move engines, but it makes complete sense that they would want to, because they seem to do a very effective job of unloading work from the GPU, which can only help performance further. Even saying all this, of course the PS4 has the power edge, but this idea that Durango is made even weaker by the fact that it will somehow also be difficult for developers to leverage the available power is pure sensationalism.
Durango may not have the most raw power, but it will be a very easy system to design for, and it's an especially appropriate design for Microsoft's needs, as it seems well positioned for many of the things that Microsoft seemed to take advantage of effectively with the 360. All 4 move engines are capable of performing tiling and untiling, which is just a perfect evolution of tiling that is used so heavily on the Xbox 360. It couldn't hurt to help to try and assist developers in alleviating the costs of tiling. It makes complete sense, and if the 360 is any indication, tiling will be a heavily used feature. What's more, a Radeon 7970, for example, comes with 2 DMA engines. All 4 of Durango's Move Engines each have a DMA engine, thus doubling the amount. The DMA's purpose in the 7970 is to allow for more efficient use of available bandwidth by allowing 2 streams of data simultaneous use of both directions on a pci-express link. Durango being able to handle 4 streams of data in both directions is something developers will likely find helpful. The peak performance gets divided between the 4 (more realistically 3 in most instances, since Move Engine 0 is partly shared with the system, but it can also help out with games as well), but that doesn't exactly make them any less useful.
And, finally, considering that games will be played off of the hard drive with every game installed on Durango, it also has to help that one of the move engines has a dedicated LZ decoder for decompressing compressed data on the hard drive. That's essentially what's going on with Durango. The Move Engines don't somehow make developing games more complex, as they can be idle if I wish, and Durango would still perform well in games. Will some developers use Move Engines better than others? Absolutely, but they don't hold Durango development back, they aide it. And I haven't even touched on another very helpful feature of Durango's GPU, the 3 display planes. The main one reserved by the system basically decouples system rendering from game rendering, meaning that the console OS can not only be at a different resolution from the game, but more importantly, the OS can run at a steady frame rate, even if there was a situation where a game was not. On the 360 right now if a game is demanding to a certain degree or is even experiencing unsteady frame rates, this also impacts the performance of the system OS. Durango apparently fixes this. But more than that, the display planes can further assist to reduce memory and bandwidth consumption if developers take advantage of each display plane's ability to use multiple image rectangles. Each display plane can handle up to 4. May even work well with tiling, too?
Again, not something that hurts development, but that likely aides it more than it hurts it using specialized hardware. Microsoft have built a damn good system. Just because they've apparently done quite a bit of customization to their console's GPU, doesn't mean that they've made development dramatically more difficult. They have not. There are basically 3 customizations on Durango's GPU.
4 Move Engines.
3 Hardware Display Planes
32MB of Low Latency ESRAM in place of traditional VRAM.
With all these customizations, I think it makes sense that they structured Durango in such a way that the ESRAM's memory bandwidth belongs exclusively to the GPU and doesn't have to be shared with the CPU, like the DDR3 bandwidth is. Raw power may not have been Microsoft's intent with Durango, but they still find themselves with a powerful system regardless that is essentially like a swiss army knife of very useful sounding customizations. And this is all before the potential development benefits of that low latency ESRAM and the possibilities that may exist for some wholly unique approaches to certain aspects of development.