They were popular in different periods. The 19th century was the heyday of Impressionism, while abstraction was popular in the 20th century. And although impressionism does not pursue complete realism, it still follows the principle of imitating nature, while abstractionism is completely divorced from this principle.
Impressionism and abstractionism are separated from the painting style of complete realism. Their main difference is that although impressionism does not pursue complete realism, it is still based on reality and draws with the instantaneous impression of nature.
The abstract school is completely divorced from the principle of imitating nature. It takes the painter's imagination and intuition as the starting point of painting. It rejects those symbolic and illustrative means of expression.
Impressionism reached its peak in the 1970s and 1980s, while abstraction was the most popular artistic style in the 20th century.