The nuclear data forms a vital component in reactor core physics computations. The nuclear data is evaluated and modified on a continuous basis by different nuclear data centres and laboratories worldwide. The work on upgradation of the nuclear data is being carried out using new evaluations obtained through experiments and theoretical models to enhance their accuracy. Use of different sets of cross-section data in the analysis of a benchmark problem is a source of strong feedback for further improvements in data by mutual comparison of results. These comparisons also help to find out the best evaluated cross-section data released. Towards this objective, an attempt has been made to inter-compare JEF-2.2 and JEFF-3.1 evaluated nuclear data through the Monte Carlo simulation of VVER-1000 MOX Core Computational Benchmark. This study deals with the calculation and inter-comparison of reactor parameters such as multiplication factors, cell average and assembly average fission reaction rate distributions estimated for various reactor state descriptions specified in the benchmark. Point-wise cross-section libraries processed from the JEF-2.2 and JEFF-3.1 evaluated data are used in the analysis. Concerning the multiplication factors and fission rate distributions, considerable differences are observed between the two libraries. While performing the MCNP calculations with JEFF-3.1 data, it is observed that the deviations of effective neutron multiplication factors (k_eff from those of benchmark standard MCU results are lower by about ~0.100% for the most of the states than those computed using JEF-2.2. Fission rate distributions using JEFF-3.1 data are also found to have significant deviations up to ± 9.2% compared to calculations with its earlier version JEF-2.2 data. Some interesting trends on the used nuclear data are identified from the discrepancies of the individual results. The cause for considerable changes in the calculated parameters are analysed and an attempt to correlate the observed changes to the cross-sections of the relevant nuclides in the two nuclear data evaluations is made.