This paper discusses the effect of context on mobile usability, proposes an expanded model of mobile application context, and conducts an empirical study to test a number of hypotheses concerning the use of software implementation technology and location context in mobile applications. Four different application types (PC web based, PC device based, mobile web based and mobile device based) were tested using a within-subjects repeated-measures design. The results demonstrate that by utilising client side processing and location context, the mobile device based application is able to achieve objective performance and subjective usability measures comparable to those of the PC based versions, despite the limited input and display capabilities of the mobile device. Conversely, the mobile web based application, which was unable to take advantage of location context or client-side application code, showed the lowest quantitative performance.