I think the use of only one term implies a level of universal understanding.
Personally, I just call it marriage. And I use whatever term they use to refer to each other (partner vs. husband/wife). People know what marriage means. Across all cultures, it maintains the same basic premise (the benefits may vary between locales, but the gist is the same). Partnership may be a better option as far as inclusivity and equality goes, but it also presents a level of ambiguity that marriage does not. Are we business partners? Are we cops? Cowboys? With marriage, no matter what you leave off or tack on to the front of it, it is still marriage and the relationship it implies is understood without needing clarification.
The same kind of understanding doesn't exist for most of our community related terms. Within the community, sure. But when we involve cisgender people, not so much. Especially when we speak only in acronyms. I'm not sure we could get to the point as a community where we collectively agree on what terms we want to use.