Thermoblade is 40 damage per hit, Prawn arm is closer to 50 (but idk if that’s both or together, it just says 50 damage per second on the page) but given the advantages of the Prawn suit, it’s probably better to use it unless getting a Stasis Rifle involved.

Yeah, but the Prawn arm can be spammed with both arms, can be upgraded to a drill, and lets you breathe underwater, while defending you. Easily the better choice.

As I said, better unless using a Stasis rifle, which is the one thing you can’t use while in the Prawn.