Hi Aneez,
In a nutshell:
-- TestComplete provides much more powerful tests environment (logging, parametrization, etc.);
-- TestComplete can do also functional testing that is absent is SoapUI;
-- TestComplete has problems with testing web services that use encryption, certificates, etc.;
-- HTTP load testing functionality is removed from TC9 and is available as a separate LoadComplete product;
-- SoapUI requires Java to be installed on the test box and highly depends on its modules (like any Java application).