The Construction Industry (CI) contributes to 2.7 GT of CO₂e annually, underscoring the need for sustainable solutions, and 3D Construction Printing (3DCP) can assist in reverting through on-site and off-site methods. On-site 3DCP minimises transportation emissions by extruding concrete in-situ, making it ideal for large-scale projects. In contrast, off-site 3DCP, provides high precision, consistent quality, and reduces material waste, benefiting essentially modular construction. In this article, a study of both methods was made, evaluating the process following the key parameters: printer mobility, material use, energy consumption, logistics, workforce and emissions, employing a detailed multi-criteria analysis that integrates environmental, economic, and technical dimensions. The case study selected is the built on-site prototype by Havelar, which is then compared with three location scenarios to evaluate on-site VS off-site printing to assess prefabrication efficiency and compare the emissions from material extraction to building completion (LCA stages A1–A5), using a cost-per-ton CO₂ metric. The findings indicate that on-site 3DCP is optimal for reducing transport and adaptability. In contrast, off-site is excellent in precision and modularity, and long-distance travel lowers transportation costs. This study advances the understanding of 3DCP’s role in sustainable construction, supporting the transition to net zero and aligning with Construction 4.0 goals.