Developing a theme from scratch or using HTML is a good option if you want to create a unique and customized look for your website. However, there are some important considerations to keep in mind before embarking on this journey.

WordPress Theme Development:
Developing a theme from scratch using WordPress requires knowledge of PHP, CSS, and WordPress template tags. It is a complex process, but it provides complete control over the design and functionality of your site.

To get started, you can download a blank WordPress theme or a boilerplate like Underscores, Sage, or Starkers. These provide a basic structure and set of files that you can build upon. From there, you can customize the theme to fit your specific needs.

One of the advantages of developing a WordPress theme from scratch is that you have the freedom to create a design that is tailored to your brand and website goals. You can choose the layout, colors, typography, and other design elements that align with your vision.

HTML Theme Development:
If you already have an HTML site, you can convert it into a WordPress theme. This process involves converting the HTML/CSS markup into PHP templates and adding WordPress functions and template tags.

Converting an HTML site into a WordPress theme is more straightforward if you have experience with HTML, CSS, and PHP. You will need to learn about the WordPress template hierarchy and how to create templates for various parts of the site, such as the header, footer, and content areas.

One advantage of converting an HTML site into a WordPress theme is that it allows you to take advantage of the powerful features and functionality that WordPress offers. You can easily manage content, add new pages, and make updates without having to edit HTML files directly.

Considerations:
Whether you choose to develop a theme from scratch or convert an HTML site, there are some important considerations to keep in mind:

1. Time and Effort: Developing a theme from scratch or converting an HTML site into a WordPress theme requires a significant amount of time and effort. It is important to allocate enough resources to complete the project successfully.

2. Technical Expertise: Both options require a certain level of technical expertise in PHP, CSS, and WordPress. If you are not familiar with these technologies, it may be beneficial to work with a developer who has experience in theme development.

3. WordPress Coding Standards: It is important to ensure that your theme follows WordPress coding standards. This ensures that your theme is secure, performs well, and is compatible with future versions of WordPress.

4. Compatibility with Plugins: Consider the compatibility of your theme with popular WordPress plugins. Some plugins may require specific template files or functions to work properly, so it is important to plan for this during the development process.

5. Responsive Design: With the increasing use of mobile devices, it is crucial to make sure that your theme is responsive and displays properly on different screen sizes. Test your theme on various devices and screen resolutions to ensure a seamless user experience.

Conclusion:
Developing a theme from scratch or converting an HTML site into a WordPress theme can be a rewarding and creative process. It allows you to have complete control over the design and functionality of your website. However, it is important to consider the time, effort, and technical expertise required for the development process. Ensure that your theme follows WordPress coding standards, is compatible with popular plugins, and is responsive to different devices. Testing your theme on a local development environment or staging server before deploying it to a live site can help identify and fix any issues before they impact your users.