Posts that pass these checks are normally approved without being read by a human moderator. Some items may be off-topic and still get approved by the software. Details of how the moderation of h.p.o is handled are provided in the FAQ mentioned under question 3.2. Concerns about how h.p.o is moderated should be either e-mailed to the moderator or posted to that group. In contrast, many servers carry all humanities.
Some servers also store posts for humanities.
Still, the alt. Volume - h.p.o typically has more posts per day than a.p.o. The answer depends on what you want, based on the differences discussed above. Those with access to both may participate in both, if they so choose. Like many alt.