Due to the rigidity of Puppet Putty, it is quite a bit harder to shape the clay puppets. This means younger animators may find it difficult or frustrating to work with the regular formula of Puppet Putty – there is also a soft version that I did not try out. You can also melt down the clay in a double boiler and add petroleum jelly (as recommended on the packaging) to permanently soften it.
Puppet Putty is $5.50 per block online versus a similarly sized Van Aken block at $3.57 in store. Bear in mind, they are about the same amount of clay, but Van Aken is significantly more dense. What you are paying for is a product specifically designed for animation.
Before using, I condition clay by rolling it out – no matter the brand. Puppet Putty definitely requires more work to get a smooth consistency, but once it is rolled out a couple minutes, it proves to be as smooth as Van Aken. If you don't condition the clay, you will wind up with lighter spots which prove more difficult to smooth out – so take a minute or two to roll it out if you do buy Puppet Putty!
Ultimately, the best clay is the one you are most comfortable with. I strongly believe Puppet Putty is a great medium to work with if you want to animate, but that doesn't mean that I haven't seen tremendous works done with Van Aken Plastalina or Super Sculpey or Fimo. It all depends on what you are going for! I know that if you give it a shot when animating, you will be able to achieve a lot more than you would be able to with other brands with less work.
If you want to give Puppet Putty a shot, you can order some from Stop Motion Store.