As of now the difficult for PoW block (Block #127803) is 183694752.0, and for PoS block (Block #127804) is 10.4918556213. Why are the two values so different?

Is there any relation between PoW difficulty and PoS difficulty?

"This block reward reduces by half every time the hashing power of the network increases by 16 times". Does this statement apply to only PoW difficulty or to both PoW and PoS difficulty?