I definitely want to provide clients with an editable format. They paid for it so they should have that benefit. I only provide gif and jpg as mockups.
As far as I know both all three formats (when saved properly from Illustrator) is perfectly editable in Illustrator with layers maintained. All three are perfectly acceptable by print shops. Since all three format essentially have the same capabilities, there is no reason to send all three. It would be too big via email. I can only send one via email.
Another reason is that giving three will confuse clients. They keep asking "How come there is three?", "Which one do I give to print shops". etc.
I'm just curious as to which format is the "industry standard". For example, I heard rumors that "EPS is dead" (superceded by AI and PDF formats). Not sure if this is true.
If I'm going to transmit more than one file via email. I rather transmit one color version and one black/white version instead of two different formats that essentially have the same capabilites.