You're right, with on PS4 it being GDDR5. It leaned towards graphics, not system, requirements. Not exactly the breed you'd find in regular stuff.

The primary difference between GDDR and DDR is 128bit vs 64bit bus. GDDR is also normally SRAM, but DDR can be SRAM, but it is normally DRAM.

Saying one is geared to graphics is just marketing.

I think you meant SDRAM not SRAM?

So why did they choose GDDR then?

I'm not Sony Engineering so IDFK

GDDR5 trades latency for thoughtput

XboxONE DDR3: 68GB/s CAS 7

PS4: GDDR5: 127GB/s CAS 15

The reason GDDR is normally used in GPU's is the workloads are more predictive, you are doing the same calculation thousands of times, just iterating across a buffer. This is why SIMD/Cache prefetching shine in GPU's. It makes memory latency not as important.

So, you're saying GDDR is more geared towards operations done commonly in graphics? ;)

No. I'm saying it is gear to work loads with easily predictable or cache-able memory access patterns.