Are you talking about sticky putty, concerning the grey one? If so, its big difference is that it is also meant to stick miniature parts together instead of glue, and it has a setting time under 5 min, what makes it perfect for fast conversions, or when you have to fill huge gaps, and cant wait to let the normal puttys set.
Hope i could help!
Lord Flasheart: And always remember - if you want something, take it! Bobby!
Bob Parkhurst: [enters] My lord?
Lord Flasheart: I want something.
Bob Parkhurst: Take it!
[she undoes her shirt - exeunt]