Which is better?

A dismissal under Penal Code section 1000 is better (that is my opinion of course). When a person is granted PC 1000 in a case the pronouncement of judgment does not occur, so if you successfully complete PC 1000 the case is dismissed under that section. However, under Penal Code 1203.4 you must be convicted first and then you can apply for the relief available under Penal Code 1203.4.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship

In my opinion, PC 1000.

Look at PC 1000.4 for what a dismissal of a case after successful completion of PC 10000 means:

1000.4. (a) Any record filed with the Department of Justice shall
indicate the disposition in those cases deferred pursuant to this
chapter. Upon successful completion of a deferred entry of judgment
program, the arrest upon which the judgment was deferred shall be
deemed to have never occurred. The defendant may indicate in response
to any question concerning his or her prior criminal record that he
or she was not arrested or granted deferred entry of judgment for the
offense, except as specified in subdivision (b). A record pertaining
to an arrest resulting in successful completion of a deferred entry
of judgment program shall not, without the defendant's consent, be
used in any way that could result in the denial of any employment,
benefit, license, or certificate.
(b) The defendant shall be advised that, regardless of his or her
successful completion of the deferred entry of judgment program, the
arrest upon which the judgment was deferred may be disclosed by the
Department of Justice in response to any peace officer application
request and that, notwithstanding subdivision (a), this section does
not relieve him or her of the obligation to disclose the arrest in
response to any direct question contained in any questionnaire or
application for a position as a peace officer, as defined in Section
830.

An expungement (aka dismissal through 1203.4) simply puts a note on the entry in your criminal history that the case was subsequently dismissed. Yes, you can tell private employers you've never been convicted of a crime, but your criminal history will show the case, the conviction and the subsequent dismissal.