The Red Gemini 5K is the most light sensitive Red camera with a Dual Base ISO of 800 and 2500. Because of the larger photosites, its resolution is 5K instead of 8K on the Epic-W. One of the advantages of this is that it allows you to shoot in 4K at 100fps with only a small sensor crop, ideal for 4K slowmotion shoots or even in 96fps at 5K.
Another advantage is that the sensor is 18mm tall, useful for shooting anamorphic. Besides RAW, the Gemini can also shoot ProRes internally up to 2K. This camera has no built-in NDs, so do not forget to order these as well.