Absolutely. We encourage our clients to hold in-house training session if they have 5 or more participants. The main reason is that it helps focus on your organization and your industry specific issues, problems, and challenges. Your employees will find it easy to discuss their specific issues.
However, there are also benefits in attending a public course. The biggest value is that you get to see what are best practices, issues, and challenges being faced by other organizations and/or industries.