Neither model is a universal winner because they’re very similar in massage style, comfort, and overall buyer sentiment. The Zyllion ZMA-34 is the better fit for most “set it up in a chair and use it often” households, thanks to plug-in power plus two-speed/rotation controls; its main limitation is being tethered to an outlet. The Zyllion ZMA-13RB is the better choice for people who want real flexibility and plan to use the massager away from outlets; its main limitation is battery management and mixed runtime/heat feedback.
With either one, the biggest practical caution is durability—offset by consistently strong pain-relief feedback and repeatedly positive warranty/support experiences.