"consultative" is used with a word like "committee" to convey that it lacks the authority to act. i.e. It would give (or contain in the case of a document) recommendations which would be taken into account by the acting body. "consulting" would never be used that way. "consulting" is just a general term used in business to describe expertise that has been hired from outside the firm. The study groups are consultative, but the General Assembly rarely enacts regulations that conflict with their recommendations. His consulting firm offers both regulatory and marketing services. The consulting engineer can only sign the waivers if he has written authorization from the Board of Directors.

Maybe in business language, the usages are twisted a bit (that tends to happen) but generally, -ive means it IS something while -ing means is is DOING something. So an informative document IS the information it contains while a supporting pillar in a building is DOING the support. You can also BE supportive for someone, in which case you ARE the support for that person while you are also supporting them because you are doing that action. In that case both really mean the same but the difference is in how you use the word. It can be very subtle :D

It is a consultative business. (It's very formal and lees frequently used) But NOT a consulting business. I am a business/ finance/ legal/ engineering consultant. I am a lawyer/engineer I do consulting. I consult to government.