I know serial is easy to use. Plug it in, set the baud rate, Data Bits, Parity, Stop Bits, and Flow Contol (unless you tell your Butel Arc software to poll it for you), and then maybe the radio setting are correct too. Hmmm... BCD996T/BCT15, front port or back? What about the cable, do I need a Null-modem adapter???.. And so on...
*Icom* now uses USB ports on the IC-R20, IC-R/PCR-1500/2500 and provide the USB driver.
If you use a USB/Serial adapter, you need a driver. As the older computers with serial die off, you still need a driver for the new one with USB ports.