Interfacing to a Windows web service advice

[eluser]Flayra[/eluser]
All the options send using plain text over a secure (SSL/HTTPS) connection, so one is not safer than the other. SOAP is basically just XML with an additional layer. In this case, you should use what's easier for you - XML is more readable, but the plain Name/Value pairs is probably easier to read.

The COM example is just, from what I can make of it, a simple HTTP Post Request with XML data to a server URL.