This is a situation in which I think using a generic qualifying term, instead of a term indicating incorporation, would be preferable—IF it's determined that qualification is needed at all. If "Pantone" isn't sufficient, then I'd want to use "Pantone (Firm)", with "Pantone, Inc." and "Pantone, LLC" as variants. I don't see any benefit to having separate AAPs for "Pantone, Inc." and "Pantone, LLC". My hunch is that the change from "Inc." to "LLC" is related to a merger or acquisition; in fact, I wouldn't be surprised if maybe Pantone, Inc. was dissolved and Pantone, LCC was created as a "new" company.
Of course, there are also those cases where two levels of hierarchy have the same base name. What I'm used to seeing is the creation of something like "Useless Corporation, Inc." become a subsidiary of a newly created "Useless Corporation Holdings"—and then that new parent gets absorbed into some other entity, or otherwise changes its name. So, I suppose it is possible that Pantone, Inc. and Pantone, LCC both existed simultaneously at one time? If that's so, it become a little trickier, but there is certainly precedent in AACR2 for putting both under the same established heading, with variants for the specific entities.
Don't you just love all these games corporate bodies play...
Kevin M. Randall
Principal Serials Cataloger
Northwestern University Library
Proudly wearing the sensible shoes since 1978!