Muscular or Slim? - A humanoid Mantis Shrimp

[Sqwiid]

I've been drawing what I would perceive as a humanoid version of a Mantis Shrimp! It's more of a artistic rendition than scientifically accurate, however, I did get into a small "tiff" with a friend on whether a humanoid Mantis Shrimp would be muscular or slim. I drew mine to be rather muscular, most obviously within the arms, as I said they would be larger for the those infamous punching skills, they said they'd be slimmer so they can move faster, claiming the punch relied more on speed than actual strength/power.

Any secondary opinions or theories on this? For added context, the humanoid is significantly larger than the average Mantis, being around 3-4ft tall (I haven't settled on the height yet.) AND I've covered the humanoid in plated armor with some exposed skin bits.