AP Computer Science A vs. OCP
First, I applaud your ambition!
The first OCP exam covers roughly what AP did until this most recent year, when the college board stripped out Interfaces. I would still suggest that they are mostly equivalent, but there are a few practical advantages to the AP Test:

It is substantially cheaper.
Colleges recognize it for admissions purpose. (As you point out, an admissions officer is unlikely to have heard of the OCP, and would question how it compares to AP, and why you didn't just take AP)
Many colleges, at least in North America, automatically award credit or alter your course placement based on your AP scores. No equivalent system exists for OCP.
Because OCP is a professional exam, and you are unlikely to join the profession for at least 5 years (assuming a 4 year college), the exam may be considered dated by the time you get into industry, and it seems obvious that a college major will count for more than the lowest-level Oracle exam in any case. TBH, I've never heard of anyone asking for job applicants to provide Oracle scores, though I imagine that it probably happens somewhere or they wouldn't still offer the exam.

One last thought for you: you do not have to take the course to register for the test, so you can self-study. If you wish to go this route, but your school won't allow you to register yourself for the exam without being enrolled in the course, you should still be able to sign up at a different location.
Good luck!