(with the same hardware support)
Haiku's architecture is more organized and optimized. With the same level of hardware and software support Haiku always wins over Linux or Windows or MacOS. Haiku is based on BeOS, witch was and still is modern tech OS, and Linux, Windows and MacOS is based on older tech ideology, why is so bloated software there...
Haiku feels fast, because it uses preemptive multitasking, it is very modern thing.
...For OS architecture (how parts of OS are organized how they interact with each other and with user) programming language is secondary thing, you can rewrite Haiku in asembler and still Haiku would feel and work like Haiku (maybe only faster and more eficient).