DataReader-It  is used to fetch/read data from a database in a much faster way. Since the rows are fetched one at a time, load on the network will be low. Since DataReader is read only,.Since it support forward only data iteration, random data fetch is not supported.

DataSet – it is an in-memory representation of a table in a database. Dataset takes lot of application memory compared to DataReader. It is slower compared to DataReader. It also support querying.