A seam is small, but it is never truly invisible
Every non-vase-mode perimeter has to start and stop somewhere, and that transition point, the seam, leaves a small visual artifact: a slight bump, a Z-scar, or a thin vertical line depending on your slicer's seam settings. The three common ways to place it, aligned to one consistent edge, aligned to the load direction, or randomized across the surface, each solve a different priority and can conflict with each other on the same part.
How the choice works
If hiding the seam is the priority and a specific cosmetic face is designated, aligning the seam to a hidden or back edge is the direct answer. If minimizing strength impact is the priority, or the load would otherwise cross a naive seam placement, aligning the seam parallel to the load direction takes priority, since a seam is a small local discontinuity best kept out of the load path. Absent either of those pulls, a randomized seam strategy scatters the artifact across the surface rather than leaving one consistent line.
Worked example
A designated cosmetic face, hide-the-seam priority, no load crossing concern: the tool recommends aligning the seam to a hidden or back edge, with load-direction alignment shown as the alternative in case a later strength requirement changes the priority.
A common mistake
A frequent error is choosing a seam strategy once for the whole print job and forgetting that different features on the same part might actually want different strategies. An outer wall with a cosmetic face and an internal structural rib do not necessarily benefit from the same seam placement logic; consider whether your slicer lets you vary the approach by region rather than applying one setting globally.
Limitations
This is a qualitative tradeoff comparison between the three common seam strategies; it does not calculate the actual strength impact of a seam at a specific location or guarantee a specific visual result, both of which depend on your slicer, material, and print quality.