Based on the meaning of the C band and Ku band, the first obvious difference is the frequency. And The frequency of a wave is inversely proportional to its wavelength. As we all know, the low frequency has longer wavelength while the waves with a high  frequency has a short wavelength. Generally, the Ku band comes with much higher singal strength in area of spot beams. It means that the signal can be received on much smaller dish antennas. And the C band system uses bigger antennas because of the longer wavelength.

The second difference is the dish antenna that receives the frequencies. Prime focus dishes are used to receive C band frequencies, and the smallest commercially available prime focus dish is 1.8 meters. Offset dishes are used to receive Ku band and the smallest offset dishes are only 60cm in diameter. Due to the diameter of antenna, the installation area is also different. The C band with the focus dish requires enough area.

When to use the C band & Ku band is another difference. C-band is preferred in some locations where rainfalls are heavy such as some districts in Africa. From a commercial standpoint, C-band is more suitable for satellite applications that require greater bandwidth while the Ku band is more suitable for satellite applications that require smaller bandwidths.

Both C band and Ku band could be used in satellite applications. Because of the higher frequencies, higher data transfer rates & smaller antenna, the Ku band is used widely now. And Ku band is less susceptible to variations in weather and interference caused by the leaves of trees and other terrestrial interferences, therefore the signal received by Ku band is more stable.