The other consideration that is rarely mentioned is that retaining the clutch allows small amounts of misalignment without damage.
A completely solid coupler, the slightest misalignment will cause tiny flex with each revolution and eventually break something... especially if you have welded something together and not hardened it afterward.
If you go clutchless, SOME couplers have spirals, or plates, or rubber bumpers designed to handle some mis-alignment. The rubber ones are generally bad news at high torque. The metal plates work well, but add back almost as much weight as you take out with the clutch.