Start with the water path, not the product
A French drain and a swale can both move water, but they are not interchangeable. The practical difference is whether the problem is mainly visible surface flow, shallow subsurface wetness, concentrated roof discharge, or a missing outlet.
Quick route screen
Use this to decide what deserves measurement first—not what to install.
When a swale is easier to inspect
A shallow swale keeps flow visible, so blockage, erosion and standing water are easier to notice. It is worth screening when surface runoff is the main problem, enough width exists, and there is continuous fall to a lawful stable outlet.
When subsurface collection may fit
A French drain can make more sense for a narrow wet strip or shallow seepage where surface shaping would interfere with use. It still needs verified fall and an endpoint; burying perforated pipe does not create an outlet.
Roof water is a separate case
If the job is simply moving concentrated downspout water, a solid conveyance pipe or surface extension is conceptually different from a perforated collection drain. Releasing roof water through perforations along the route can put water back where you were trying to remove it.
Failure modes to compare
Swales can erode or lose grade. French drains can clog, become hard to inspect, or be installed without enough fall. Either option can create a new problem if it discharges toward a building, septic system, public right-of-way or neighboring property.