While many Elementor users have considered Thrive Architect an Elementor copy, they seem to forget that Thrive came way before Elementor did.
Yes, there are many similarities, but the same could be said in reverse.
This is a tough comparison and I think, for some, it is going to end up coming down to cost.
Elementor is an annual license cost, where Thrive Architect comes with lifetime updates.
Also, it is important to note that Elementor is a lot more refined and much better suited for full website builds.
Elementor Pro is also more powerful in that it allows you to create dynamic headers / footers and post templates.
Elementor also has an ecosystem around it of 3rd party plugins to expand its features.
Thrive Architect has a great focus on marketing with specialized features like timed content, popup boxes, and deep integrations with the other plugins that Thrive makes.