PanelView Standard terminals can only use their network port for communications to controllers. If you have a PanelView Standard that has an Ethernet port as well as a serial port, the serial port can only be used for upload/download or as a printer port.
PanelView Plus terminals can use any installed port to communicate to controllers. The connection path is defined in RSLinx Enterprise, on the "Target" tab.
Post the exact part number of the PanelView you are using.
In general, an Ethernet connection is much faster than an RS-232 serial connection. Why do you intend to switch ?