Large gut Echinoderms

OK, you keep your bum!  This does mean it costs more muscle energy to digest food as it has to move against gravity, but your gut is longer, so perhaps you get more out of it. But it's definitely good enough.

In fact, if you are going to push food right through you, it might make sense to make the gut bigger and bigger so that it can extract as much energy and nutrients as possible from your food.

Should my bum look big?
Yes
No

Blind gut Echinoderms

Quick win: no bum!  You can get away with a smaller gut, and eat, absorb the easy nutrients, and chuck up whatever's left, then go on to the next thing.  You'll need to be able to collect lots of small food items.

With your smaller gut, you can afford bigger arms.  This could make it easier to move, by making them longer, or make them more effective by branching each arm into many arms.

Longer
Wider