This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
I feel more than performance you must be more interested in reliability as this is a payment processing and a loss of data will be totally undesirable.
JMS will provide you reliability whereas threadpool will be an in memory solution (provided you do not persist your queue. If you do, you are trying to implement JMS )
So, definitely i will go for JMS.