Part strength is a function of both material and 3D printing process. Parts made of metal material will inherently be stronger than parts made of most plastics and resins.
Both laser sintering (LS) and extrusion (often known by the Stratasys trademarked term Fused Deposition Modeling (FDM)) can create strong parts.
LS can offer an advantage in strength because the process sinters the layers of a part. One could say that LS offers 100% infill, which enhances strength. LS parts can have strengths equivalent to injection-molded parts.
Extrusion parts can also demonstrate strength, especially if a part takes advantage of infill patterns. The disadvantage of infill is that it requires more material, and thus can increase the cost of a part. Even so, extrusion creates good bonds between the layers, but not quite on par with laser sintering. And don’t forget that extrusion primarily uses plastics and resins as the build materials.
Several vendors offer charts and information on material elasticity, elongation at break and tensile strength, along with the recommended 3D printing method.