It's mostly an effort to bring down cost. Different manufacturers of DVD and hard disk providing a bulk buy of components at different prices. Tech changes and the chipsets evolve (usually for the better). It's not just the PS3 and Xbox 360, certainly the PSX, PS2 and Xbox had several hardware changes over their lifespan,…
They are all the same machine, and play the same games. Only difference is the extras. Nothing has changed over time. All consoles go through the revisions to their chipsets over the years. There's about a dozen models of the NES and Genesis systems alone. But it makes no difference, they all work the same and look the…