Slop.

Generated by AI Hexbear attracts a broader, more meme/shitpost-oriented leftist crowd. Users tend to be highly engaged, irreverent, and active in culture-war and international-news megathreads. The instance is known for very high comment volume and a chaotic, humorous vibe that some outsiders find off-putting (hence frequent defederations). It feels like a lively, tight-knit leftist meme hub.

Lemmygrad.ml: More strictly Marxist-Leninist and theory-focused, with strong emphasis on pro-China, anti-imperialist, and geopolitical content. The userbase is dedicated but smaller and generally less meme-heavy/more serious. It has a larger number of local communities dedicated to specific socialist topics or regions. Often described as the "classic tankie" instance.

Overall: Hexbear has the bigger, more energetic userbase by most metrics (total users, activity, content volume). Lemmygrad is smaller but punches above its weight in organized Marxist communities. Both remain tiny compared to general-purpose instances like lemmy.world (which has tens of thousands of MAU). If you're looking for raw leftist engagement, Hexbear wins on size and vibrancy; Lemmygrad feels more focused and "pure" ML.