Background Customized cutting guides are technical aids that make primary pelvic bone tumor resection safer and more reliable. Although the effectiveness of such devices appears to be widely accepted, their conception and design remain varied. Two main designs have been reported: the heavier block-type customized cutting guides and the lighter patch-type customized cutting guides. As recent tools, there must be more evidence regarding the impact of design on their accuracy and ergonomics. Thus, an evaluation of their respective performances appears warranted. Questions/purposes In a cadaver model, we assessed whether (1) a thinner, patch-type customized cutting guide design results in resections that are closer to the planned resections than the heavier block-type customized cutting guides, and (2) the patch-type customized cutting guide design is more ergonomic than the block-type customized cutting guide with improved usability in surgery (in terms of bulkiness, ease of placement, primary and secondary stability, and stability during cutting). Methods We conducted an experimental study involving five fresh whole-body anatomic specimens (three women and two men with a median age of 79 years and median weight of 66 kg) by simulating six virtual tumors in three areas according to the Enneking classification (Zones I: iliac wing, II: periacetabular area, and I and IV: sacroiliac joint area). We compared the impact of the customized cutting guide’s design on performance in terms of the resection margin accuracy using CT scan analysis (deviation from the planned margin at the closest point and the maximum deviation from the planned margin) and the intraoperative ergonomic score under conditions simulating those of an oncologic resection of a bone tumor (with a range of 0 to 100, with 100 being best). Results The patch customized cutting guides performed slightly better than the block customized cutting guides regarding deviation from the planned margin at the closest point, with median values of 1 mm versus 2 mm (difference of medians 1 mm; p = 0.02) and maximum deviation from the planned margin of 3 versus 4 mm (difference of medians 1 mm; p = 0.002). In addition, the patch design was perceived to be slightly more ergonomic than the block design, with a 92% median score versus 84% for the block design (difference of medians 8%; p = 0.03). Conclusion We observed an equivalence in performance regarding accuracy and ergonomics, with slight advantages for patch customized cutting guides, especially in complex zones (Zone I and IV). Owing to a small cohort in a cadaver study, these results need independent replication. Clinical Relevance The patch-type customized cutting guide with thinner contact spots to the bone in specific areas and less soft tissue dissection might offer an advantage over a larger block design for achieving negative oncologic bony margins, but it does not address issues of soft tissue margins.