The decision on whether to use responsive design or a dedicated mobile site depends on the nature of your website. It not only impacts the appearance of your site, but also how you implement business strategies, especially if it's a commercial endeavor.
Responsive design is ideal for simple websites that don't require intricate user experiences, such as company profiles or landing pages.
However, when developing complex applications, carefully consider how users will interact with every aspect of the site. Keep in mind that implementing responsive design may demand more resources compared to a separate mobile site. For e-commerce, social media, and other sophisticated applications, opting for a mobile version might be more beneficial.