Thank you, nursing OPEN HOUSE interview--snail mail or e-mail?

Went to a nursing open house; spoke with asst manager (at length) and unit manager (briefly). The thank-you notes are the problem!

Snail mail: Always safe, but may be stuffy (i.e.., not giving out the "fast-action-do-it-NOW" image); may stick out better mentally

E-mail: Incredibly timely; allows them to save MY e-mail immediately for future communications (could be a plus).

The interviews were done on a walk-in basis (resume was NOT pre-submitted).

Also, would it be a good idea (or overkill?) to drop a note of some sort to the recruiter? The hospital is really pushing the idea of "customer service", and keeping people/staff happy by finding out what they need and providing it.

Thanks!