IIRC OpenURLParams was introduced because the parameter list of OpenURL became unwieldy. Assuming there is enough overlap, I'd say way can join the two.
Technically, OpenURLParams is used to communicate from content to the embedder, and LoadURLParams is used the other way round (and inside content). However, the embedder ends up converting the OpenURLParams to LoadURLParams anyway when calling back to content to make the navigation.
best
-jochen