Marielene

Even when you check all you adjustment layers one by one (to avoid anarchy :-) ? (de-activate all and re-activate one by one) 

When I open my edited photo in ACR as object photoshop, it seems I can go back to ACR any time to make changes. Please correct me if I'm wrong :-)

Absolutely! Thanks for your feedback :-)

But, yes, the conclusion is that the difference isn't noticable, as you write in this course :-)

Oh? 
This is what I found on a forum: PSD files are usually smaller than TIFF files because the PSD format has compression built into it to make the files smaller. This is lossless compression, and doesn't affect the contents of the file - you can open it, save it close it numerous times without affecting the quality of the image it contains.

TIFF files are not as compressed (if you choose LZW compression) or aren't compressed at all if you don't compress them, and so are much larger, but contain the same information about the image they contain.

If the files are only going to be used by you, save them as PSD files, but if you're going to exchange them with other family members, the TIFF format may be better as it can probably be opened by more different software than can the PSD files.

Lately I heard a professional photographer say that TIFF files contain more information, PSD compressed and deletes certain information. You say there's no/hardly any difference.

What about it? Thanks!