In satellite communications, narrow spotbeams can provide high power and data rates to the desired location while reducing spatial interference. Advanced transmission antenna technology is critical to generate and switch narrow beams rapidly among a large number of users under quality of service (QoS) constraints such as average delay. In this paper, we jointly optimize resource allocation and congestion control, and compare the performances of two types of satellite transmit antennas: a multiple beam antenna and a phased array antenna. For a multiple beam antenna with traveling wave tube amplifiers (TWTA), throughput is decided by either the most demanding user or the average of all user parameters. For a phased array antenna, joint antenna gain patterning and beam scheduling is given as a function of channel conditions, interference (depending on users' geographical distribution), and average delay requirements. We then develop a low-complexity on-line algorithm of choosing either interference suppression or sequential service for the active users who are closely located within the width of a spotbeam. Due to flexible power allocation, the phased array antenna can provide better performance than the multiple beam antenna when a small number of users are very demanding or many users are densely crowded in a small area.