I've been working on some graphic works on photoshop and I always saved a PSD version as the draft file and a TIFF version as the product image, but I noticed that there seems to be virtually no difference in just using TIFF to edit things on photoshop again because the layers are preserved. Should I only save as TIFF if I want to keep things clean?
Also, why should I rasterize/flatten image before printing as the final product? What is the difference between flattening and rasterizing an image?
Layered TIFFs are are completely arbitrary custom sub-format of the TIFF spec and e.g. PS layers must not be the same as "layers" exported from a CAD program. Using it as a standard storage format would be pretty foolish, especially considering that other programs may not at all be able to open such files. If anything ever changes, you end up sitting on a stockpile of potentially unusable files, especially if at one point you may no longer use PS or you use an old version while the rest of the world has moved on. At least with the PSD format there will always be a minimum of backward compatibility as long as the maximum compatibility option is used. I know a ton of programs that can deal with PSDs of that kind, but only a handful that can deal with layered TIFFs. The rest I don't understand. Why would/ should anyone flatten images before printing? That's what the printer driver does. One would only do so manually if the printer driver is unable to natively translate specific features e.g. PostScript Printers not being able to deal with some transparency stuff... Otherwise there is no requirement whatsoever to flatten the image or rasterize dynamic content layers.