I have used both. Ignored both timesThe complaints section probably do not get involved in individual cases. I assume you used the complaints, compliments and feedback form.
We used the partner visa enquiry form, which goes to the relevant visa department. That probably helped to produced a faster 801 for us.
Some people, who don't get a response from that, then do a complaint about not getting a reply from the visa department, and the complaints section can get involved with that.
The complaints section do say they will not respond to general enquiries about departmental processes.