Getsitecontrol is the more common of the two in our index: it runs on 157 websites against 6 for Riddle. Counts come from real scans of each site's home page, not vendor claims, and cover the sites in TechLookup's index rather than the whole web.
Getsitecontrol is a form and popup builder.
Riddle is a platform enabling creation of lists, polls, and quizzes.
Within the surveys sites we have indexed, Getsitecontrol holds 15% and Riddle 0.6%.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.