Does it really matter whether your logging program starts first and then the rig is fired up - or whether the rig is fired up and then the logging program is opened?
If your transceiver is a recent model (IC-7200, UC-7410, IC-7600, IC-9100, TS-590, TS-990) that includes a USB interface that emulates a virtual serial port, and you're using this USB interface to connect your computer to your transceiver, that virtual serial port will not exist before you power up the transceiver. In this case, it will be easier to power up the transceiver before you start an application that communicates with your transceiver. If you your transceiver is connected to a serial port or USB-to-serial-port-adapter in your computer, then it shouldn't matter whether the transceiver is powered up before or after such an application.
73,
Dave, AA6YQ