categories – WordPress speed: hierarchical vs non-hierarchical taxonomies?


I'm in the process of creating a site that will eventually host thousands of messages, all of the same type of personalized "Artwork" message.

Each blog post is assigned multiple custom taxonomy terms, such as "Artist", "Project", "Art Director", "Format" and more.

I have read that too many taxonomies and / or terms can slow the page down. So I don't know if I should build a structure with many non-hierarchical taxonomies, or with only one or two hierarchical taxonomies but more terms and child terms.

Many taxonomies, mostly non-hierarchical:

 • Artist Taxonomy (non-hierarchical): 1000s of terms (1 per post)
 • Formats Taxonomy (hierarchical):
   – Formats Terms: 4 terms (1 per post)
     –Format Child-Terms: 15 terms (1 per post)
 • Projects Taxonomy (non-hierarchical): 100s of terms (1 per post)
 • Artdirectors Taxonomy (non-hierarchical) 100s of terms (1 per post)
 • Genres Taxonomy (non-hierarchical): 20 terms (1-3 per post)
 • Collections Taxonomy (hierarchical):
   – Collections Terms: 50 terms (0-1 per post)
     - Collection Child-Terms: 100-200 terms (0-5 per post)
 • Publisher Taxonomy (non-hierarchical): 30-40 terms (0-1 per post)

against.

Less taxonomies, but hierarchical:

 • Artist Taxonomy (non-hierarchical): 1000s of terms (1 per post)
 • Meta/Collections Taxonomy (hierarchical):
   – Formats Terms: 4 terms (1 per post)
     –Format Child-Terms: 15 terms (1 per post)
   – Projects Term:
     – Project Child-Terms: 100s of child-terms (1 per post)
   – Genres Term:
     – Genre Child-Terms: 20 child-terms (1-3 per post)
   – Artdirectors Term:
     – Artdirector Child-Terms: 100s of child-terms (1 per post)
   – Collections Term:
     – Collection Child-Terms: 50 terms (0-1 per post)
       – Collection Grandchild: 100-200 grandchild-terms (0-5 per post)
    – Publisher Term:
       – Publisher Child-Terms: 30-40 child-terms (0-2 per post)

Is there any advantage / disadvantage of either of these two structures with regard to website speed? I fear that it will become slow once thousands of messages are on the page.