The blog post explores the performance disparities between different Ruby interpreters, specifically MRI Ruby, JRuby, and TruffleRuby, focusing on their application in building Jekyll sites. Despite expectations that JRuby and TruffleRuby would offer speed advantages due to their Java Virtual Machine (JVM) foundation, MRI Ruby consistently outperforms them in practical scenarios like Jekyll builds. JRuby's slower performance is attributed to its complex start-up processes and the need to manage Java threading, which is not inherently thread-safe for Ruby's built-in types. The author discusses various optimizations, such as the use of the --dev flag and JVM tuning, which can mitigate some of the performance issues but not completely overcome MRI Ruby's efficiency. The post also highlights the strengths of JRuby and TruffleRuby in CPU-bound, long-running applications and suggests testing different Ruby runtimes to find the best fit for specific use cases. The article concludes with community feedback and ongoing efforts to enhance JRuby and TruffleRuby's performance for real-world applications.