Round parachutes are less likely to spin and foul in whatever mess you have that made you use it. Add a ram-air parachute to an existing wad of crap, and you're more likely to die. The opening times of rounds and squares are the same. But it's not about deployment time - it's about safety. If you can't handle a round parachute, then you shouldn't be paragliding. Besides, there's nothing much to handle with them - they're easier than a ram-air. If you can handle a ram-air, then a round is nothing to worry about.
Note, dear readers, that this is about paragliding. I'm not criticizing the use of square reserve parachutes in skydiving operations.
