The Polycolor pencils are cheaper alternatives to brands like Polychromos and Prismacolor, and although they don't perform quite as well I would class Polycolor as a strong budget contender if you're not in a position to lay out a lot of cost.
You can see this comparison on paper when you blend two colours, applying hard pressure, because the Polycolor pencils produce a similar dark speckle to Prismas when too many layers are used. Out of the three, they are the most difficult to blend.
The pigment feels buttery to lay down and doesn't need a lot of pressure to produce deep colour. They're not as soft as Prismas, but I think they're better off for it. Extremely soft pencils may create lucious results but I find them a lot less value for money as they deplete so quickly. Polycolor pencils seem to be the happy medium between soft and hard, and for just over £20 for a tin of 24 they're relatively cheap without compromising on quality.
Here is a little picture I coloured with the Polycolors to show you some quick blends that can be done without too much effort.