Why is the alimentary canal (such as in humans) more efficient at digestion than a gastro-vascular cavity?

Question

Why is the alimentary canal (such as in humans) more efficient at digestion than a gastro-vascular cavity?

Answer 1

Specialization - you can have different sections of the canal focus on specific tasks.  In example, the mouth and stomach regions perform more of the physical breaking down of food, and then the intestines deal with the chemical breakdown and absorption.  Digestion is more efficient than in a gastrovascular cavity, where the food is only broken down into small fragments, enters the cells, and is chemically digested within the cell.

Answer 2

CAUSE IT IS A CANAL I DON'T NOW WHAT AMI TYPING