In DPDAs, only one move is possible when reading any input from any state but, in NPDAs, there can be multiple moves possible for an input symbol from a state.
In Deterministic Push Down Automata it is always defined that at for a particular input it will be going to a specific state but in case of Non-deterministic Push Down Automata for a specific input it may go to different states ...
So , NPDAs are more powerful than DPDAs.
There are Context Free Languages, such as the language of palindromes, that can be accepted by NPDAs but not by DPDAs.