What is the relationship between EB- 1C and L- 1A?

According to many years of American immigration experience, EB- 1C and L- 1A are the same thing in principle, but there are also differences.

When we applied for EB 1C, the sponsor was an American company. The American company recruited his executives from overseas affiliates and came to the American company to continue to be executives. Then, there are two ways for American companies to let executives work in American companies. The first is a non-immigrant visa-L-1A, that is, to apply for temporary work permits for foreign employees and foreign executives; The second is that American companies help foreign executives to apply for permanent work permits, that is, green cards, that is, EB 1C green cards. There is a big difference between the two in detention. Non-immigrant visa L 1A is valid for 7 years at most, and the green card is permanent.