Which do you prefer, SOAP or JMS?

Since you don't know the motivation behind this question, the best strategy is to respond truthfully and accurately. This enables the interviewer to evaluate your response in the context of their operations. You can confirm this by asking a clarifying question after you provide your answer. This may lead to a discussion about the suitability of the methodology their organization currently uses vs. incorporating some new ideas into their web designs in order to improve their operations.

"While I used to advocate for the java messaging service, I now prefer SOAP in my web architectures. While it enables distributed communication that is loosely coupled, reliable, and asynchronous, SOAP is more flexible because it allows distributed elements of an application to communicate a variety of lower-level protocols, including HTTP. SOAP can use a JMS-compliant transport with SOAP messages to enable interoperability between the implementations of different vendors."