Both senior software architects have a long experience with leading architecture projects. Depending on a project's demand, they are acting independently or as a team. With their different specializations they support each other where appropriate.
Software architects work on the coarse-grained structure of a software system.
Such structure has typically less impact on the functionality of a system than on qualities such as reliability or fault tolerance, extensibility, robustness against specific changes in the environment, adaptability to changing demands, etc.