Both the Amazon Cube and the Echo Shows provide Video Calling features. The difference:
Echo Shows permit "Drop In" (or as I use them) Routines to initiate a video call from the Loved Ones... WITH NO LOVED ONES INTERACTION REQUIRED.
Amazon Cube requires your loved one to TURN ON the camera regardless of which way the video call is initiated.
This is why Echo Shows are required ... or optionally as in my case... a combination of both as seen in the short clip below. Note the Echo Show on the wall for Video Calling and Calendar Reminders and always showing photo slides of her family and the TV (Amazon Cube driven) showing a Live Cam of A Bald Eagles Nest in California. Mom loves watching live cams.