there are three things to consider when evaluating a grasping methods
- what is the range of objects it is able to grasp?
- how simple is it to construct?
- how easy is it to control?
1 DoF scissors
These are super popular for upper limb prosthetics, and are good at most tasks used to evaluate effectiveness of prosthetics, aside from using scissors, ironically. these are completely reliant on friction, and have the small downside of having no indication of the size of the object in the grasp since an object closer to the point of rotation will open the grasper as much as a larger object further out.
Parallel jaws
these have more contact area than scissors but a smaller range of motion. They can be hard to control precisely, and some tasks may require both pads to contact simultaneously - a tall order.
There are some variations such as the 4-bar linkage jaws, which move up and in rather than just in. There are also multi-fingered hands which are already common in industry. they are useful for grasping cylinders from above, for instance, but the extra digits makes them worse at tasks like pinching.