First, the time is different: China's Qixi Valentine's Day is the seventh day of the seventh month of the lunar calendar, while the Western Valentine's Day is February 14th of each year. This is a very obvious difference.
Second, the origins of the festivals are different. We all know that my country's Qixi Valentine's Day comes from the romantic love story of the Cowherd and the Weaver Girl, and comes from the unforgettable love between the Cowherd and the Weaver Girl, also known as the "Qiqiao Festival"; while the Western Valentine's Day is also called "Saint Valentine's Day", which is one of the traditional festivals in the West. This festival is to commemorate two martyred saints of the early Christian church named Valentine.
Third, the customs are different. During the Qixi Festival, many girls worship the gods and beg for cleverness, and compete for cleverness as the main festival activities, while on the Western Valentine's Day, lovers send each other chocolates, greeting cards and flowers to express love or friendship.
I think the main differences between the two Valentine's Days are in these aspects, of course you may have different opinions.