For the most part if you stick to the restriction enumerated in the WS-I Basic Profile 1.0a with regard to the generated WSDL, or the source WSDL,
you should be fine.
A while back most wonks recommended always starting with WSDL, because that was the easiest way to get interoperability. That's still true to some extent, but the javaToWsdl tools are better now so you can pretty much go either way. Just make sure you examine the generated WSDL to make sure that it complies with the WS-I BP. This will require that you understand WSDL - but that's the expectation for anyone who is taking the
test.