  This study presents a comparison between the Sprint Z3 and A3 head parallel
kinematics machines, distinguished by their joint sequence. The analysis
focuses on performance attributes critical for precision machining
specifically, parasitic motion, workspace capability, stiffness performance
over the independent and parasitic spaces, and condition number distribution.
Although these machines are extensively utilized in precision machining for the
aerospace and automotive industries, a definitive superior choice has not been
identified for machining large components. Moreover, the distribution of
stiffness across the configuration of parasitic space has not previously been
addressed for either mechanism. This research reveals that despite identical
parameters used and exhibiting similar parasitic motions, the Sprint Z3
demonstrates superior stiffness, workspace volume, and condition number
distribution. This performance advantage is attributed to variations in joint
and link sequence, which enhance deflection resilience, crucial for
manufacturing large-scale components. This also results in a higher condition
number and a larger workspace. The result highlights the importance of design
architecture in the efficacy of parallel kinematics machines and suggest
