## 5 Conclusions  
This study provides an in-depth, head-to-head comparison of Fused Deposition Modeling (FDM) and Stereolithography (SLA), based on identical test geometries and standardized methods. By assessing surface quality, dimensional accuracy, mechanical properties, production cost, energy consumption, and environmental factors, we illustrate how these prominent additive manufacturing (AM) technologies align with different requirements and constraints. Overall, the results demonstrate that each technology excels under particular conditions. SLA offers precise dimensional tolerances--around \(\pm 0.05\) mm--and the smoothest as-printed surfaces (\(R_{a}\approx$2.2\,\mathrm{\SIUnitSymbolMicro m}$\)). Its higher tensile strength (up to 69-70 MPa) can be advantageous for applications needing strong, rigid parts. Yet these benefits come at a higher cost per part, a slower throughput, and a more complex post-processing workflow, where uncured resin demands careful handling and disposal. In contrast, FDM demonstrates significant advantages for cost-sensitive or rapid prototyping scenarios, with typical build times almost half those of SLA and part costs that can be reduced by more than 50%. While the resultant prints may be limited to \(R_{a}\approx$12-13\,\mathrm{\SIUnitSymbolMicro m}$\) and dimensional deviations closer to \(\pm 0.15-0.20\) mm, this slightly coarser finish remains acceptable for many engineering prototypes. FDM further stands out for its simpler waste management, particularly if biodegradable PLA is used, as opposed to SLA's resin-based waste, which is generally hazardous in its uncured form. From a mechanical perspective, FDM parts--especially those printed with ABS--offer a somewhat lower tensile strength but better ductility, which translates to greater tolerance for dynamic or impact loading. Meanwhile, SLA excels in load-bearing applications that demand high strength and finer detail, provided the brittleness of the material does not undermine part performance. In terms of reliability, FDM experienced more nozzle-related issues and warping, yet SLA's occasional print failures often resulted in more time-consuming cleanup. Looking to the future, research may focus on exploring advanced filaments (e.g., carbon- or glass fiber-reinforced) and high-performance SLA resins (e.g., high-temperature or impact-resistant) to refine the balance between mechanical properties and cost. Additional studies on wear, fatigue, or UV resistance would help quantify long-term performance, bridging the gap from short-term testing to real-world applications. Investigations into hybrid approaches that combine the rapid throughput of FDM with SLA's superior surface quality are also of interest. Furthermore, comprehensive life-cycle assessments (LCAs), paired with decision-making tools such as AHP or TOPSIS, could offer deeper insights into sustainability across different production scales. In conclusion, neither FDM nor SLA emerges as outright superior for all applications. Rather, each approach meets particular needs, depending on criteria such as dimensional tolerance, surface smoothness, mechanical strength, production budget, and environmental considerations. By clarifying these trade-offs, the present research can guide practitioners toward a more informed selection of AM processes--maximizing functional performance while balancing cost-effectiveness and sustainability. Writing--original draft, M.A. and P.M.; Supervision, P.M.; writing--review and editing, P.V. and J.S. All authors have read and agreed to the published version of the manuscript. **Funding:** This work is funded by National Funds through the FCT--Foundation for Science and Technology, I.P., within the scope of the project Ref. UIDB/05583/2020. Furthermore, we thank the Research Center in Digital Services (CISeD) and the Instituto Politecnico de Viseu for their support. [PERSON] thanks the national funding by FCT--Foundation for Science and Technology, I.P., through the institutional scientific employment program contract (CEECINST/00077/2021).