difference between COM port and SATA
COM ports are the common name for EIA-232 ports (aka RS-232), i.e. ports where only the lower levels of communication are defined: physical (mechanical and electrical) and data link.  

For SATA these are different, and SATA defines also network and transport layers, which means packaging and error detection/correction. You can run a protocol on CMO ports which do this too, but they're not part of the COM specification itself.