It comes down to personal preferences - with handwritten notes leading slightly by 52% versus electronic notes at 44% based on a survey. Our advice is to take the recipient into consideration and chose the form of your message from there.
Whether it is handwritten or electronic, make sure the note is personalized and sent promptly after the interview. It is another marketing piece to sell yourself, a chance to remind the employer what your skills are and how they benefit his or her company.
Mind Your Manners: A Job Seeker's Guide to the Thank You Card
The Lost and Dying Art of Saying “Thank You”
The power of a thank-you note