STL stores geometry only; PLY and OBJ can also carry colour. A scanner with open STL/PLY export lets you work with any lab and any CAD package; proprietary formats tie you to one ecosystem.
From our data: 31 of 68 devices in our database are documented with open file export.
Differences between the formats
STL describes a surface as triangles with no color or texture and is accepted by virtually all CAD, CAM and printing software. PLY adds color per vertex, which helps with margin marking and shade communication. OBJ carries geometry with a separate texture image.
DICOM is a different kind of file: volumetric X-ray data from CBCT. Implant planning combines a DICOM volume with an STL or PLY surface scan.
Open export in practice
Check whether export is included or needs a paid subscription, whether files leave the vendor cloud without a per-case fee and whether the scan can be sent directly to the lab or aligner company you use.