ZDNet UK has a comprehensive analysis of factors businesses should consider when choosing between 3G or Wi-Fi for mobile workers: The conclusion should be disheartening for operators of either network. Based on comments from an analyst, the writer concludes that some companies might be better off asking workers to use Internet cafes, which are more prevalent in Europe than in the U.S. Companies might be wise to wait for a bundled Wi-Fi/3G offering because both services are lacking individually. In the same breath, however, he notes that such bundled offerings probably won't be available for a while.
Until such bundles are available, it's true that 3G and Wi-Fi may appear competitive to the many users who aren't willing to pay for both. But choosing between the two is like choosing between two evils because both need changes to their pricing models and both are lacking coverage.