TIFF vs PSD in Lightroom

I was asked this question during a photography meetup while discussing/babbling about how I use Lightroom and why I save all my "Final" edits in the TIFF Format ... I could not remember why, but I had to do some research, since I usually don't do things for no reason.
PSD files are smaller than TIFF files because they use lossless compression that doesn't affect the contents of the file.
TIFF files are  only compressed if you choose LZW compression, if you decided not to compress them then they create a larger file. Compressed or not they contain the same information.

The main reason to use TIFF in Lightroom

  1. TIFF has better support for metadata changes/updates.
  2. TIFF is publicly documented, this is one of the reasons that TIFF a preferred file format.
  3. TIFF can do EVERYTHING a PSD can save including layers, transparency, etc. and be saved up to 4 GIGS in size.
  4. TIFF can save all the color spaces PSD can.
  5. TIFF is better for printing (so I hear)
  6. TIFF is public, even if it's owned by Adobe (by virtue of the Aldus purchase) if Adobe crashed and burned, TIFF would still be available.
  7. TIFF files file is not limited to only zip compression and can have many different ways of compression, including JPEG compressed data within a tiff file.

Main issues with PSD in Lightroom

  1. PSD can't be saved with Maximum Compatibility as they can't be previewed in Lightroom (kinda negate the workflow benefits of the space savings).
  2. PSD is a proprietary format that few third party programs can read it.
  3. PSB is the new Photoshop "native" file format for images beyond 30,000 pixels.

PSD files use data compression called RLE (Run-length encoding), if you save without Max compatibility turned on, it will be a bit smaller, but current versions of Lightroom may not be able to open it. PSD is a proprietary file format, even the Lightroom and some Photoshop engineers will tell you that PSD is no longer the Photoshop "native" file format. It has no advantages and many disadvantages over TIFF.

TIFF (non compressed) is still by far more common and universal in the general industry. Unlike past file formats that had no real standard and were implemented differently.

If the files are only going to be used by you, then its fairly safe to save them as PSD files, but if you're going to exchange them with other photographers print sites, or editors, then the TIFF format may be better as it can probably be opened by more different vendors/software than can the PSD format.