This paper compares two popular VoIP systems: FusionPBX and Elastix. The first is based on Freeswitch, and the latter is based on Asterisk. The comparison is done at two dimensions: technical dimension and operational dimension. Since technical capabilities of FusionPBX and Elastix are implemented in their cores, i.e. Freeswitch and Asterisk, technical dimension, investigates these cores. This dimension also considers research studies which have suggested using cores in different VoIP applications. On the other hand, the operational dimension, performance of FusionPBX and Elastix is compared using some test scenarios, and the results are provided.