Choose pastel pencils if you are interested in portability, less dust, less mess and more convenience. Pastel pencils are chalk pastels encased in wood. They are easily blended with your finger, a tortillion, a tissue or a gum eraser. The pencils have less of the range of line that is possible with pastel sticks but they do achieve finer details that are not possible with softer pastels.
Select soft pastels if you desire more vibrant, rich colors. Soft pastels use more pigment and less binder. They are easily blended but require an application of fixative to prevent smudging.
Explore soft pastel pencils. These work well if you want the convenience and cleanliness of wood-encased pastels along with the rich, vibrant colors and smoothness of the heavily pigmented, soft pastels.
Choose semi-hard pastels to experiment with a less fragile, slightly more maneuverable pastel. Semi-hard pastels produce less dust than soft pastels but also contain less pigment so their colors are not quite as vibrant.
Experiment with hard pastels. Hard pastels are good for adding detail and for initial sketches. They do not blend as easily as softer pastels, and because they are manufactured with less pigment, they are neither as bright nor as vibrant as soft pastels.