A faster string makes a triple brent stole a LOT easier.
Sure.
Heavier string moves faster through the air than lighter string. While you certainly canāt pin speed down to a certain type of thread or a certain material, nylon threads and most all types of embroidery threads tend to move much quicker than your standard poly. Thinner threads tend to move faster then thicker threads, and thicker strings tend to move faster than thinner strings.
Itās difficult to describe why a certain string is faster than another. Iām not great at physics. However, the heavier the string, the faster it moves. More energy that youāre able to put into it, or something.
However, to say that strings donāt move at different speeds is quite incorrect. The speed at which string moves is one of the major differences in different kinds of string.
Canāt really add much to what Jake said, but Iām going to anyhow: Itās self-evident that some strings move faster than others. Itās simply physics. Not all strings are the same dimensions or weight, and they donāt have the same tensile properties. If you really need it explained to you, itās clear you havenāt really tried a variety of truly different strings (ie. not just variations on bulk poly). Or if you did, it was so long ago that youāve forgotten.
At an exaggerated scale, get yourself a length of sewing thread. Start whipping it around in a circle. Then get a skipping rope or something similar. Reproduce the same motion. The sewing thread will start to follow itself, while the skipping rope will stay more or less taught from end to end so that you can smack it against the ground. Or to put it another way: good luck skipping with a length of thread. You wonāt be able to whip it around your feet!
The same properties that make it different to whip a thread around vs. whipping a skipping rope around translate to yoyo string. The range of difference is less because yoyo string still needs to meet certain criteria. But this is whatās known as a ācounter-argumentā in formal logic. If you can prove the extreme case, then the narrower case must also be true even if on a lesser scale.
It really shouldnāt require this much explanationā¦ it seems so (hate to repeat myself) self-evident.
Iāll tell you this. Iāve been throwing for just over a year now. I have resisted slack tricks because I suck at them. Something simple like a slack trapeze still has me befuddled. And I get frustrated quickly. So I try a few times, fail and give up. But, if thereās a string out there that can help me improve faster and thus stick with practicing longer, Iāll definitely try it.
The weight difference is much more than you would think. If I compare the lightest string I make and the heaviest, the difference is probably over a gram. (At average string length. I havenāt measured grams/centimeters on my strings.)
The heavier string will let me do jade whip about twice as fast, maybe even three times as fast.
Faster string wonāt make you suddenly a master of slacks, but it can certainly help you out.
Not intending to talk down to you; it was simply quite literalā¦ it may have been a while since you tried those strings! As for the rest of the explanation, well, you asked! I wouldnāt have answered if you hadnāt asked, and I do have a tendency to over-explainā¦
Iāve been told I come off condescending at times, and I do believe people who tell me thatā¦ but itās unintentional. Still, I apologize since thatās how it came across!
Uhm, what?
Itās an objective fact that some strings are considerably heavier than others. It is also an objective fact that some strings are faster than others as well. Iām not even getting into factors that contribute to how much control the string has (attributes that actually do make complex slacks easier that at independent from speed)
I don see how this is a matter of opinion.
As for certain strings making you ābetterā at slacks, they certainly can make you be able to do more with the skill that you already have.
Itās like upgrading from a stick to a golf club. Sure, they can both do the same thing, but one makes it tons easier.
I just bought 30 strings from Jake tonight because of this thread.
So Jake, you DO win 
But I expect to be able to do no handed binds by yesterday!
I just want you to know, that if there was an award for biggest patronizing jerk on this forum, Iād be front runner. Iām a jerk, and thatās a plain fact.
That being said, you are the most patronizing person I have ever seenā¦ Anywhere. Seriously, I didnāt think anybody could be worse than some of my jerkish shennanigans, but WOW. You really stole that award out from under me, while being sincere in your post.
Iām gonna have to step up my game if I want to be the biggest jerk on the forum. You really raised the bar here.
Q, you win.
Look for twisted strings type D-Minus. Its crazy.
Most talented players can do just about all their tricks with most yoyos. However, itās nice and enjoyable to throw with a well balanced and stable yoyo. You can feel the difference.
Yes, basic poly can whip and slack, it will work fine.
Strings with a little more weight have an edge maintaining momentum. Also fibers that are slicker have less air resistance. The difference between whipping with basic poly and say a string of the same thickness made from trilobal (embroidery) thread is immediately recognizable.
Here is basic poly close up:
http://farm9.staticflickr.com/8213/8281702342_f3defe5bc4.jpg
Basic Poly Example on Flickr
And here is trilobal:
http://farm9.staticflickr.com/8480/8281705474_de76b2078b.jpg
Trilobal string on Flickr
Years ago, I used to make a trilobal string. That thing whipped like lightning, but it would slip around your finger and didnāt have bounce.
If you want a really fast whipping string, try Toxic. If you want something more moderate, try one of the other makersā strings.
100% polyester.