Which parachute round or square has the fastest drop speed?

Answer 1

You can get a square parachute to descend extremely rapidly - indeed, there have been a number incidents (sometimes involving fatalities) when skydivers 'spiralling' close to the ground have had their reserve parachutes deployed automatically by the Automatic Opening Device (sometimes call the Automatic Activation Device). Indeed, a skydiver was killed a few weeks ago in Bad Lippspringe, Germany because he turned rapidly too close to the ground.

A round parachute would, depending on your weight, let you down faster than a square on 'half brakes', although some small squares (<170 sq ft) would give you a pretty heavy bump unless you flared just before landing.