No you cannot apply to both, you must choose either CTC or Oxford. If you apply to both then only your first application will be considered. This is according to the OAA website.
To me it seems as though CTC is the obvious choice, the high likelihood of a UK base as well as the security bond coming back tax free is a big advantage. Getting any money tax free mower days is worth a lot.
Out of intrest is there anyone who has applied to Oxford on here?