I've been wondering just that. Can you help me understand why we have
the legacy EPS option? Is the CS EPS architecture actually different than
the EPS architecture of previous versions'?
The eps is the same. (unless someone in the know posts a contradiction)
A8 and earlier versions format were based upon postscript. (this is overly generalizing it)
A9+ is based upon pdf.(still generalizing)
When Illustrator saves a eps file, it writes extra data to it so that it can reopen and edit the files just as if it was saved as a AI file.
Thera are a lot of tangents I can go from here but take a simple CS document with a little bit of text and a drop shadow. Save as a CS eps file. (remember, this is a two in one file. A eps and the extra data Illustrator uses to reopen for a fully editable document)
Open this in AI 10 and you will receive an error message blah blah in cannot work. Create a black artboard and LINK place the CS eps file into Illustrator 10. Hey, it places fine and can be ripped as well. Not dupe the image on the same artboard and in the links palette, embed one of those images. What do you know, it embedded the eps and you can edit the elements. Text seems to break up similar to opening a pdf. In this case, Illustrator used the eps data to embed and not the extra instructions.
CS save for eps is actually better than any previous version. If the eps does not need to be editted, then those with previous versions of Illustrator have no need to open the files and only increase chances of problems occuring if they make it a standard practice to check the files and resave when resaving is not needed.
Other issues that require prepress to be able to go into files is due to older rips which cause them to do workarounds to produce the work.