To solve the scalability issue of the traditional client-server architecture, many media streaming applications have adopted Peer-to-Peer (P2P) architecture in their implementations. Because of the success of using TCP in client-server streaming applications, most P2P streaming applications also use TCP as their transport protocol. On the other hand, some researchers argue that UDP is a better choice of transport protocol, as it is light-weight and meets the requirements of real-time streaming. However, there is no comparison study of using two transport protocols in global deployment of P2P applications. In this paper, we describe our efforts along this line. We first describe the designs of two P2P streaming systems: one using TCP, and the other using UDP. To simulate real deployment scenarios, both systems are developed based on similar designs used in current popular P2P streaming software products and comparative experiments are carried out on PlanetLab, a global Internet simulation platform.