POS:
Block generation is no longer determined by the computing power, but the stake held by the node has the final say. This solves the problem of the useless consumption of POW computing resources. However, due to the unconditional trust of the representative, the node is very easy to do evil, such as nothing at stake attacks.
DPOS:
A certain number of representatives, such as 21 node representatives, are generated dynamically, and only these 21 nodes generate blocks, which reduces the probability of doing evil. At the same time, it uses post-mortem punishment to limit node representatives to do evil behaviors, but it is always not safe enough (how to punish, use collateral? How much collateral is needed? Can the losses of failed transactions caused by evil be quantifiable? If the collateral cannot be quantified, it is meaningless), and the confirmation speed is indeed slow (requires 14 blocks)