PSDVSTIFF
Both store layers. Both are huge. But TIFF is not owned by Adobe. Which one is safer for archiving?
The Verdict
**TIFF is universal. PSD is proprietary.** If you want to ensure your grandchildren can open your file, use TIFF (LZW compression). If you live inside the Adobe Ecosystem, PSD is slightly faster.
Compatibility
Winner: TIFF
Lots of non-Adobe software can read layered TIFFs. Very few non-Adobe apps can perfectly read a complex PSD.
File Limits
Winner: Draw
PSD has a 2GB limit (then you need PSB). TIFF has a 4GB limit standard. Both are massive.
Compression
Winner: TIFF
TIFF offers LZW or ZIP compression which is very efficient. PSD RLE compression is faster but larger.