This paper introduces programmable arrays of optically inter-connected electronic processors and compares them with conventional symbolic substitution (SS) systems. The comparison is made on the basis of computational efficiency, speed, size, energy utilization, programmability, and fault tolerance. The small grain size and space-invariant connections of SS lead to poor computational efficiency, difficult programming, and difficult incorporation of fault tolerance. Reliance on optical gates as its fundamental building elements is shown to give poor energy utilization. Programmable optoelectronic multiprocessor (POEM) systems, on the other hand, provide the architectural flexibility for good computational efficiency, use an energy-efficient combination of technologies, and support traditional programming methodologies and fault tolerance. Although the inherent clock speed of POEM systems is slower than that of SS systems, for most problems they will provide greater computational throughput. This comparison does not take into account the recent addition of crossover interconnect and space-variant masks to the SS architecture.