Elementor is the more common of the two in our index: it runs on 924 websites against 255 for Polylang, and 61 sites use both. Counts come from real scans, not vendor claims.
Elementor is a website builder platform for professionals on WordPress.
Polylang is a WordPress plugin which allows you to create multilingual WordPress site.
61 sites run both Elementor and Polylang. That is 24% of the sites using Polylang, the smaller of the two.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.