PSD files can work for archival purposes as well, but one needs to be careful which features are compatible with other products.
For example, Photoline supports the most common colour adjustment layers, and imports those without issues. Even text layers are partly preserved (converted to a hidden text layer, and a bitmap version). Layer effects are for the most part also compatible. Layer masks also work without a hitch. But obviously not everything is supported, and newer CC functions will also be problematic. All in all, however, PSD offers more support for Photoshop's "special" functionality to be preserved than TIFF.
Since Photoline is still compatible with Windows 2000 and OsX 10.6, and has a very small installation footprint (can even be installed on a usb stick), it might be a good fall back solution for those users who wish to be able to open their PSD files with the most important base functionality still intact.
With TIFF one must tread carefully, because "layered" TIFF files are a Photoshop construct, and not all software supports those properly. Only non-layered TIFF files are completely compatible in my experience.