Mobile Internet users have two options for connectivity: pay premium fees to utilize 3G or wander around looking for open Wi-Fi access points. We perform an experimental evaluation of the amount of data that can be pushed to and pulled from the Internet on 3G and open Wi-Fi access points while on the move. This side-by-side comparison is carried out at both driving and walking speeds in an urban area using standard devices. We show that significant amounts of data can be transferred opportunistically without the need of always being connected to the network. We also show that Wi-Fi mostly suffers from not being able to exploit short contacts with access points but performs comparably well against 3G when downloading and even significantly better while uploading data.