Many assumptions have been made about positive effects of the object-oriented paradigm on software quality. It has been also widely assumed that the object-oriented programming technique is powerful than conventional procedural programming technique and object-based languages provide abstraction far better than procedural languages. However, in reality little or no empirical evidence has been given to support these assumptions. Therefore, there is a desperate need for a quantitative-based comparative evaluation of merits of object-oriented versus conventional procedural program design methods and languages. This paper reports on a pioneer work in this direction. The paper describes the results of application of well-established software metrics on data-collection through controlled experimentation, where forty subjects developed program samples in Java and C languages for solution of the same set of problems via object-oriented and procedural structured program design methods respectively.Three important aspects of Program Quality known as program difficulty, effort to comprehend implementation of algorithm and level of languages have been measured from Java and C programs using well established and recognized software science metrics. These metrics have been reported powerful to objectively assess the three aspects mentioned above. Our experimentation has objectively indicated the strength of OOP and OOPL against conventional procedural programming method and languages on firm quantitative basis. The study also hints that software metrics and previously established techniques in Software Engineering for experimentation can be nicely used to evaluate quality of OOP and OOPL. This provides basis for further investigation to evaluate effects of various other aspects of OOP and OOPL on programming process. The proposed work can be extended towards many avenues.