Digital without a doubt.

• More convenient to travel with it
• Awesome how the e-ink looks just like paper and draws little energy
• Your entire library can take much less space
• Save the trees
• If it gets damaged, only your device will be destroyed, but your library (hopefully) remains (if you make backups)
• Instant access to basically any book (no need to wait for delivery or in-person shopping)

To me, my Kobo was one of the best investments I've ever made. Before buying it, I didn't really read many books