Well...sort of, but not really.
A personal prelature is headed by a prelate (Bishop Javier Echevarria in the case of Opus Dei) and it does not have geographic limits (unlike a local diocese which does have geographic limits), but includes persons who are associated--this is why it's called "personal." Moreover, it envelops both clergy and laity. It's not a religious "order" because it has a lay element.
A personal ordinariate is similar but different. It is headed by an ordinary (who can be either a bishop or priest). It too is "personal" meaning that it does not have geographic boundaries like a diocese does. It can also include both clergy and laity like a personal prelature. A personal ordinariate differs from a personal prelature in that an ordinariate is reckoned as a "particular church." The military "archdiocese" of the United States is an "ordinariate" and not really an "archdiocese."
Caveat: I'm not a canon lawyer and so I may have fudged some details. However, I think that this give a general explanation as to how the two canonical bodies are similar and different.
[See also: New Video on Pope's Anglican Ordinariates]
Yours in Christ,