The most apparent difference between the two methods is the time till ready to use. Tangzhong can be used as soon as it cools to room temperature while Yudane should be rested for about 8 hours. Yudane is simpler to make however, incorporating Yudane into the dough is more difficult since the mixture is stiffer.
The hardest part is the math involved to get your recipe to 75% hydration before using either method.
Tangzhone Recipe needs to be 75% hydration % of total flour 5 to 10% Flour to liquid 1:5 Ready to use once cooled Mixture - like rough | Yudane Recipe needs to be 75% hydration % of total flour 20% Flour to liquid 1:1 Ready to use 8 - overnight Mixture - thick paste |