Tallywell.

Crab (cooked) vs Shrimp (cooked)

Crab (cooked)Shrimp (cooked)
Protein · per 100 g19.4 g24.0 g
Fiber · per 100 g0.0 g0.0 g
Energy · per 100 g97 kcal99 kcal
Protein · per 100 kcal20.0 g24.2 g
To hit 30 g protein155 g · 150 kcal125 g · 124 kcal

Bold marks the better side of each row. "Per 100 kcal" answers the density question — which food delivers more protein for the energy it costs. Portion row is computed live from the same USDA base values shown on each food page.