Make the scanning process a bit slower usually since there is some padding around each tile. E.g. if you set the tile size to N it will actually scan each tile as if it was N + P voxels wide (where P is some smallish number of voxels, usually around 3 but it depends on the character radius). Using tiles at all will allow multithreading to be used when scanning however.
Create more triangles in the navmesh. This will slow down pathfinding a bit simply due to there being more triangles to search. Having more uniformly sized triangles is good for the path quality though. Having very large and very small triangles next to each other can lead to suboptimal paths in some cases.