A larger sensor in terms of the number of pixels yields a larger print of museum quality. A larger sensor size in terms of the physical size of the sensor changes the field of vision of a given lens - if the diagonal of a sensor is twice as long as another sensor, the larger sensor will have twice the field of vision for a given lens. Practically, this means a 100-400 mm lens on a 1 inch sensor ( 24 X 36 mm) will act like a 160 - 640 mm lens on an 15 X 23 mm sensor.

A larger sensor in terms of larger physical area for each pixel yields a higher quality electronic function. the larger size pixel will have a higher signal to noise level which results in crisper, clearer pictures especially in darker areas of a photograph.

Here is a link to sensor overall size:
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=0ahUKEwic4-OJtfvUAhXE4SYKHVK-A-8QjRwIBw&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAPS-C&psig=AFQjCNGfkE3SGbVbo6QM3v-ouqEDND3jdw&ust=1499662708255896

The pixel size will be the total area of the sensor divided by the number of pixels in the sensor. My Canon T6i APS-c sensor (22.2mm X 14.8mm) has ~24 Million pixels, and a pixel size of 3.72µm square. The 5D IV has a full size sensor with 30 Million Pixels yet has a pixel size of 5.3 µm square or over twice the area of the pixels in my camera. That should work out to about four times the signal to noise ratio on the big sensor. ( of course, the 5D IV is about 4-6 times the price of the T6i too.