It really depends on what is in the PSD file. Some of what causes a PSD file to be larger is that it carries a preview within the file also. On some of my larger template files, I put a blank layer at the top to block the creation of the preview data so the file is about 25% smaller.
As with the TIFF, it also depends on what is in it. If there are more large intricate shapes with transparent areas around then (like doodles or something), then there will not be as much compression available. Typically, the compression will make the TIFF a little smaller than the PSD.
Originally Posted by donakat
I was surprised to see the comparison with the psd and tif templates that the tif files were so much smaller. However, with some other layered files (not templates with the simple large colored shapes, but with more typical layered files for a layout) being very much bigger than the psd files. What's up with that? Is that because they were saved without any compression? I did a test with a 4-layer layout, saving as both psd and tif (LZW-RLE compression), and the psd file was 79.4 mb, the tiff file was 64 mb. Is this more typical?