Slow cooking chicken (thigh), why 4 hours?
While both recipes will produce &quot;cooked chicken thighs&quot;, the intended texture of the result is different. In the case of slow cooking, the temperature is meant to be high enough to render out fat and convert collagen into gelatin. The texture of the meat itself will be somewhat stringy and shreddable, with some dryness (hopefully compensated for by the fat and gelatin). In the case of the sous vide recommendation, the result is meant to be firm rather than shreddable, with more retained moisture, and no attempt to convert collagen.
For slow cooking, the long cooking time is required to effectively render the collagen. For sous vide, you basically just want to hit the target temperature, so recommended time is lower (but can be extended without affecting things much).