henry_Kang:

However many question in here actually said that DP give better result than DDP.


No, this is not guaranteed. The only conclusion we can draw is that DP should be able to produce the same result model as non-parallel training, and DDP cannot guarantee this. But regarding which one is better, it needs to quantitatively measured, as it is affected by a lot of factors, e.g. batch size, lr, loss function, etc.