Elementor is the more common of the two in our index: it runs on 1,003 websites against 291 for wpBakery, and 20 sites use both. Counts come from real scans, not vendor claims.
Elementor is a website builder platform for professionals on WordPress.
WPBakery is a drag and drop visual page builder plugin for WordPress.
20 sites run both Elementor and wpBakery. That is 7% of the sites using wpBakery, 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.