All the standard Williams ive seen at the pod have got around late 15 secs, where as the standard 172s ive seen seem to get mid 15s/low 15s.
Of course it all depends on the driver and the launch. Williams would be lighter & therefore easier to get off the line than a 172. And as we all know power/weight is the key.
Theres no point arguing over which is better as theyre different cars for different types of people and tastes. A Talbot Lotus Sunbeam could be arguably a better car because it is faster and rear wheel drive but it would spawn different discussions im sure.
Its all banter anyway i hope