The advantages and disadvantage of a SCP can be briefly summarized as the following:
Capable of moderately high strains, can produce 49% or more.
Low weight and thinness.
Good power density; strong for its size.
Moderate force output, about 1 N per SCP string.
Increasing the force output can be done by actuating multiple SCP units in parallel.
Thermally-actuated, so actuation speed and force depend heavily on the surrounding environment.
Bending and torsional motions can be challenging to produce, and may require multiple SCP units in parallel.
Friction is a non-negligible factor in many cases
Friction between polymers fibers within the thread will bleed out energy as non-useful heat, and decrease the overall efficiency of the actuator.
Low power efficiency.
Not very fast; the highest actuation frequency in standing air is approximately 0.3 Hz.
Requires electrical current fed from both ends of the actuator. This can be difficult to implement in space-constrained designs.