Basic website re-development: Drupal or WP???

existing website needs re-design/re-development, looking towards drupal CMS. Also interested in SEO for the site. We are a small mental health care and consultancy provider, service-orientated, and would like to have our website be more flexible for us and for clients and potential clients. Online payments feature desirable as well; a place for clients' feedback (moderated), and the site made more suitable as a marketing tool to both individuals and companies that might wish to investigate our services. We are a small group at this point in time. Thank you!