Full Idea
Unlike the standard model, with its 19 free parameters (including the masses of quarks, coupling constants and mixing angles), string theories have a single free paramater: the string tension.
Gist of Idea
String theory only has one free parameter (tension) - unlike the standard model with 19
Source
Brian R. Martin (Particle Physics [2011], 10)
Book Reference
Martin, Brian R.: 'Particle Physics' [One World 2011], p.159
A Reaction
This must be one feature in favour of string theory, despite its problems.