As coaxial cables---electric cables used to transmit frequency signals for radios, TVs and computer networks---the RG6 and the RG59 differ in manufacture, application use and capabilities.
RG6: The Pros
The RG6 is thicker than the RG59, possessing a larger centre conductor (which transmits satellite/cable signals and voltage) and a dual or quad shield to reject radio frequency interference that adversely effect satellite and cable installations. The RG6 also has a larger dielectric insulator, which greatly reduces the cable's ability to conduct electricity. Indeed, it can operate to as high a frequency as 1.5 Gigahertz (GHz). Thus, as a thicker cable, the RG6 has better signal quality than the RG59; and is perfect for CATV, satellite and cable applications. Also, one can make longer runs of RG6 cable without worrying about significant signal loss.
RG6: The Cons
However, the manner in which the RG6 is manufactured prevents it for being utilised for other applications such as video projectors, component video and plasma TVs. Its shield, usually made out of foil or braided aluminium, gives it an operative range of above 50 Megahertz (MHz) and consequently deems it incompatible with the aforementioned applications that operate on frequencies below 50MHz.
RG59: The Pros
Thus, this is where the RG59 comes into great use. For instance, for High Definition (HD) TVs that only require frequencies around 37MHz (or any other applications that require lower frequencies than 50MHz), the RG59 cable is ideally designed.
RG59: The Cons
Just like the RG6, the RG59's level of thickness works against it for other applications. Since it has a smaller centre conductor, dielectric insulator, and outer shield, its signal quality is not as good as that coming from the RG6 (even if it still delivers acceptable performance for CATV). Plus, the RG59 does not have a foil shield, thus rendering it useless for satellite feeds or cable installations, and totally rules it out from reaching the GHz-level signals that the RG6 is capable of.
The RG6 is perfect for CATV, satellite and cable; and to a degree, it can be used for video frequencies, an area that the RG59 is virtually limited to. With the addition of new channels by cable TV companies and the continued advancement in communications systems, the demand for the more efficient RG6 will increase over the RG59.