This paper presents an experimental performance assessment for localization systems using received signal strength (RSS) measurements from a wireless sensor network. In this experimental study, we compare two types of model-based localization methods: transceiver-based localization, which locates objects using RSS from transmitters to receivers at known locations; and transceiver-free localization, which estimates location by using RSS changes on known-location nodes caused by objects. We evaluate their performance using three sets of experiments with different environmental conditions. Our performance analysis shows that transceiver-free localization methods are generally more accurate than transceiver-based localization methods for a wireless sensor network with high node density.