Users can access the Internet via 3G/4G cellular data networks using various types of user devices (e.g., smartphones, tablets, datacards). We conduct a detailed measurement study on the impact of different device types on the data/control-plane performance of a commercial, city-wide 3G cellular data network in China. We present a methodology that correlates different data/control-plane datasets collected at different points in the network core, and identify more than 60K devices of different types per day on average. For the devices we identify, we investigate how their commonly used Internet applications and internal heartbeat mechanisms lead to distinct data/control-plane behaviors. For example, we observe that datacard devices contribute a large volume of IP traffic in the data plane, while smartphones introduce significant resource overhead in the signaling control plane. Our measurement study provides insights for network operators to strategize pricing and resource allocation for the data/control planes of their cellular data networks with regard to the market penetrations of various device types.