<p>This study aimed to compare the quality of radiotherapy treatment plans for stomach cancer on Halcyon™ and VitalBeam^® linacs. Treatment plans were created for 20 stomach cancer patients clinically treated with Halcyon™. The same plans were retrospectively generated for VitalBeam^® under identical planning conditions. Halcyon™ plans were generated with 6 MV FFF (flattening filter-free) beams (800 monitor units (MU)/min), while VitalBeam^® plans used 6 MV flattened beams (600 MU/min), reflecting routinely used configurations and enabling evaluation of FFF versus flattened beam delivery. Conformity index (CI), gradient index (GI), and homogeneity index (HI) for the planned target volume (PTV), and dose metrics for organs at risk (OARs) were assessed. Statistical comparisons were performed using paired tests, where significance was set at <i>p</i> &lt; 0.05. VitalBeam^® achieved a higher CI for the PTV (0.70 ± 0.17) compared to Halcyon™ (0.64 ± 0.14, <i>p</i> = 0.048). GI values were slightly higher with VitalBeam^® (3.41 ± 0.39 vs. 3.26 ± 0.51) but not significantly (<i>p</i> = 0.058). HI values were similar (0.11 ± 0.04 vs. 0.10 ± 0.04, <i>p</i> = 0.308). For OARs, most dose metrics were comparable, while bowel V₁₅ was significantly higher with Halcyon™ (374.6 ± 215.8&#xa0;cc vs. 346.6 ± 205.9 cc, <i>p</i> = 0.007). It is concluded that Halcyon™ and VitalBeam^® provide comparable VMAT quality for stomach cancer. VitalBeam^® achieved better target conformity and bowel sparing, while Halcyon™ maintained overall efficiency. These differences reflect the multi-leaf collimator (MLC) design and beam setup, highlighting clinical equivalence and tailoring machine choice to needs.</p>