The 4x TB has always had twin fan design and better speaker system. This has been the case for the last 4 years.
They also use 28W CPU vs 15W CPU in the 2x TB units. Always have.
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Depending on the workload (as shown on the video), for most use case, the double fan design will dissipate heat better (d'oh) and they will operate cooler and more silent too boot.
However, when you are stressing the CPU at 100% on both machine, the 4x TB model can be louder (since they have 2 fans) but also shown on the video, they sustain their power level better than the 2x TB model with single fan design