We show that stoichiometric LiNbO3 crystal containing nonstoichiometric defects much less than congruent LiNbO3 exhibit some advantageous properties for the holographic data storage (HDS) applications. This was confirmed by the two-beam coupling experiment and digital hologram test. In order to interpret the high performance of stoichiometric LN, we compared some related parameters such as linear electro-optic constants, photoconductivity and photovoltaic constants between stoichiometric and congruent LN crystals. In all measurements, the stoichiometric crystals grown by the novel double crucible CZ method were found to be more excellent as HDS medium. This superiority was obvious at the geometry using the extraordinary polarization.