None of the other image boards listed receive as much traffic as 4chan.
8chan is known to have users post content that has violated US and international law in the past.
These Image boards do not have membership however controversial individuals such as Patrick Wood Crusius have posted on 8chan in the past. 
None of these image boards are illegal in the US.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence