Unfortunately, the predominant use in a particular location wins this argument as there is no logical reason for using one form over the other. For instance, we say electric guitar but electrical engineering. Who's to say that electric engineering and electrical guitar are grammatically wrong.
Unlike Spanish and French, English does not have an academy of scholars who meet to decide on these things, based on grammar or etymology or whatever.
Another example is heart transplant and heart transplantation. Strictly speaking heart transplantation would seem to be more correct. But when Christian Bernard, a South African, performed the worlds first successful one in 1967 (I think), it was reported as a heart transplant and that stuck.
Another example is where British people say London Transport as the title of a public body, whereas Americans might say London Transportation which would seem to describe in the name, what the said public body does.
The best advice, in cases like these where there is no logical right reason, is to say whichever is most widely used in your cultural background and be true to who you are.