As Grids become more available and mature in real world settings, users are faced with considerations regarding the efficiency of applications and their capability of utilizing additional nodes distributed over a wide area network. When both tightly coupled clusters and loosely gathered Grids are available, a cost effective organization will schedule applications that can execute with minimal performance degradation over wide-area networks on Grids, while reserving clusters for applications with high communication costs. In this paper we analyze the performance of the NAS Parallel Benchmarks using both MPICH-G2 and MPICH with the ch p4 device. We compare the results of these communication devices on both tightly and loosely coupled systems, and present an analysis of how parallel applications perform in real-world environments. We make recommendations as to where applications run most efficiently, and under what conditions.