In the vast landscape of web development, one platform has been steadily emerging as a powerful and efficient tool for building dynamic web applications - Ruby on Rails, colloquially known as Rails. As a result, there's been a surge in demand for top-tier Rails developers. Hiring a top-notch Rails developer, however, isn't as straightforward as it may seem, but there are systematic steps that can guide you through the process.

Firstly, let's take a step back and understand who a Ruby on Rails developer is. Simply put, a Ruby on Rails developer is an individual who utilizes the Ruby programming language and the Rails framework to design and build web applications. The Rails framework, with its emphasis on Convention over Configuration (CoC) and Don't Repeat Yourself (DRY) principles, provides a structured and efficient way to develop web applications. A mastery of both Ruby and Rails is what sets a Rails developer apart.

The "what" here refers to the skills and knowledge that a top-notch Rails developer should possess. Apart from proficiency in Ruby and Rails, knowledge of front-end technologies like HTML, CSS, and JavaScript is essential for a well-rounded developer. Furthermore, a grasp of databases, SQL, and MVC (Model View Controller) architecture is also crucial, giving the developer the ability to design and manage complex data models. Familiarity with testing tools and version control systems, particularly Git, is another key skillset.

The "where" refers to the platforms and avenues to find potential Rails developers. Numerous online platforms, such as LinkedIn, GitHub, StackOverflow, and specific job boards like RubyNow, can provide a broad pool of candidates. Additionally, local Rails or Ruby groups and meetups could offer a more niche and targeted source of potential hires.

The "when" is contingent on the needs and timelines of your project. It's crucial to have a clear understanding of the project scope and the developer's role in it. For a short-term project or to add a specific functionality, a freelance Rails developer could suffice. However, for more extensive projects or longer-term engagements, hiring a full-time developer or a development team might be more prudent.

As for the "how", the hiring process should be meticulous and structured. This often involves creating a comprehensive job description, screening resumes, conducting preliminary interviews (to gauge communication skills and culture fit), technical tests or coding challenges (to assess their practical skills), and finally, detailed technical interviews. Using a pair of interviewers for the technical interview can provide a balanced perspective and prevent personal biases.

The "why" is possibly the most profound question. The reasons for hiring a top-notch Rails developer are manifold. A skilled Rails developer can integrate complex functionalities into your application, optimize its performance, and ensure its scalability, directly contributing to the overall success of your project. Furthermore, they can provide valuable insights and recommendations, contributing to the project beyond just coding.

However, it's essential to understand that like all technologies, Ruby on Rails has its trade-offs. Its advantages include speedy development due to its lean code base, a large and active community, and mature libraries (gems). However, it may not be suitable for highly computational tasks and could be slower compared to other technologies like Node.js or GoLang, indicating that the project's nature should dictate your choice of technology and consequently, the developer.

In conclusion, hiring a top-notch Rails developer is a process that requires a clear understanding of your project needs and a systematic approach to candidate screening and selection. The benefits of having an expert Rails developer on your team are significant, from delivering a high-quality application to contributing their expertise to your project's broader vision.

Remember, the key isn't just to hire a Rails developer, but to hire the right Rails developer. And as with all things of value, this requires time, effort, and a strategic approach.