Try to invoke one with cfhttp and see how you make out.
In terms of performancewise which tag is best(cfinvoke or cfhttp).
I don't mean to add additional confusion - but you can also consume web services using CreateObject(). The nice thing is that it allows you to store the web service reference object as a variable so you can make multiple method calls in a given CFM template without re-invoking the web service. Not sure how CF handles multiple cfinvokes of the same web service behind the scenes, so it might not actually buy you any efficiency.