Is WordPress better for a small firm and Joomla better for a large firm?
It varies on requirements and what is available as extensions or modules on each platform, accordingly in consideration of time, budget & resources.
Whether to develop a capability/extension requires assessment, as solutions may already be available for purchase or be downloadable as open source.
As per cost on WordPress many extensions are based on a yearly fee, while on Joomla are purchased once. Developing an extension/application requires experience and an understanding of impact on one's business.
WordPress is the most popular of platforms. Pagebuilding solutions alleviate a lot of the front-end design work using pagebuilding tool extensions such as Elementor for WordPress and JoomShaper’s SP PageBuilder for Joomla.
Joomla has an advantage in multilingual support given how menus can be created for each language and how articles/pages are assigned to each menu.