Gutenberg editor is developing fast and provides you with several workflows. They are totally different and it’s not a simple question of which one you need to choose. But let me give you some information so you can make your choice
Gutenberg (FSE) Themes
Block-Based Editing: FSE themes use Block workflow, allowing users to edit their site using a collection of blocks. This includes not just content, but also headers, footers, and other site elements. Think about each part of the site as a separate block.
Full Site Editing: As the name implies, FSE themes enable editing of the entire site, not just the content areas. Users can manipulate site-wide settings and every part of the theme directly in the editor. This includes also menus, sidebar areas, etc
Template Editing: FSE themes allow direct editing of templates and template parts through the Gutenberg interface.
Global Styles and Settings: FSE introduces global styles and settings, allowing users to define styles (like colors, fonts, etc.) across the entire site.
Simplified Code Structure: FSE themes often have a simpler file structure, relying more on JSON configuration files. You can style your theme in the editor and export it as a new theme.
The recommended theme is Greenshift free theme
Classic Themes
PHP-based Templates: Classic themes rely heavily on PHP for templating. They use a predefined set of template files (like single.php, page.php, etc.) to display content. The classic theme is based on functional components.
Customizer: The customization of site elements (like headers and footers) usually takes place in the theme customizer, not in the post or page editor. Each theme has its own customizer options and it’s very dependent on the theme, so you need to study the documentation of each theme separately.
Widgets and Menus: Classic themes use widgets and menus as separate interfaces for adding content to sidebars, footers, and other widgetized areas.
Different Code Structure: They often have a more complex file and code structure, requiring deeper PHP, HTML, and CSS knowledge. While in FSE, you don’t need to have such knowledge to build your own theme
When to choose FSE or Classic?
Someone can think, well, FSE themes have everything better, so, why do I need classic? That’s because FSE themes are something new and more experimental. While Classic themes have more than 20 years of development history so they are polished as much as possible.
So, my verdict. Do you need something that you can install and use fast with a big ready library and less learning curve? Then, Classic themes are your choice.
Do you need something where you can experiment, build your own designs, and have more flexibility? FSE block themes are your choice