It’s one of the biggest "on paper vs. reality" gaps in tech history. On paper, the PS3 was significantly more powerful; in reality, the Xbox 360 was a more balanced machine for 90% of developers.
Here is why the 360 usually came out on top during the "console wars":
1. The GPU Gap (Reality Check)
While the Cell CPU was a monster, the PS3’s graphics chip (the NVIDIA RSX) was actually weaker and less flexible than the Xbox 360’s ATI Xenos.

The 360's Secret Weapon: It used "Unified Shaders," meaning it could dynamically shift its power between drawing shapes and coloring pixels.
The PS3's Rigid Design: Its GPU was split into fixed parts. If a game needed a lot of shadows but few shapes, half the GPU sat idle while the other half struggled.

2. Unified Memory vs. The "Wall"
This was the 360's biggest win.

Xbox 360: Had 512MB of RAM that anyone could use for anything. If a game needed more textures, it took it. If it needed more AI code, it took it.
PS3: Had two strictly separated 256MB pools. You couldn't "borrow" space. If your AI code hit 257MB, the game crashed, even if the graphics memory was completely empty.

3. The "Ports" Problem
Because the 360 was basically a PC with a specialized GPU, developers wrote their code for the 360 first. When they moved it to PS3, they realized the main PS3 processor (the PPE) was actually slower than one of the 360's three cores. To make the PS3 version run well, they had to use those difficult SPEs. Most third-party studios didn't have the time or budget to do it, so they just turned down the settings on the PS3 version.
Where the PS3 actually won
The only time the PS3 truly "outdone" the 360 was in First-Party Exclusives. Studios like Naughty Dog (The Last of Us) and Santa Monica (God of War III) used the SPEs to do the GPU's job. They used that raw "supercomputer" math to handle lighting and anti-aliasing that the 360's GPU simply couldn't touch.
The Verdict: The Xbox 360 was a better gaming PC in a box; the PS3 was a specialized laboratory that required a genius to operate.