A problem with many twig stoves is their basic layout. Many are designed to lay flatter than they are tall when assembled. By that, I mean they are wider than they are tall. Heat goes up, not sideways. Stoves built to accommodate that basic fact burn better. A tall stove will allow the fire to draw.
A fire that draws properly feeds itself, and needs no auxiliary fans or bellows for air supply. It builds heat more rapidly and burns more cleanly, thereby producing more heat per pound of fuel. Ability to properly hold a large kettle with water or food is another criteria. Stability on the ground so it doesn't tip over is another.
Once these operational concerns are addressed, THEN a designer can look at weight, simplicity, cost, etc. But, operational considerations should come first.
