What’s a good brand for string tricks and looping?
???
Most all brands are good. Some brands cater more towards certain players but that neither makes them good or bad.
It depends on your price range. yoyofactory is a pretty good brand, as is yoyojam. try to stay away from yomega, unless you are just starting. with duncan, i have mixed feelings about, they are good for beginners. I hope this helps 
That’s all you need to know.
for beginners: duncan, Yoyojam, yoyfactory, yomega.
for advanced: yoyojam, yoyofactory, Crucial, 3yo3, Generalyo, CLYW, Hspin, SPYY, ILYY, and lots more.
the first list actually has yoyos specialized for beginners. the second list sells unresponsive yoyos.
some companies sell to different preferences. the fundametals by yoyofactory are all undersized, while CLYW sells ALMOST exclusively full sized. Crucial and 3yo3 sold only advanced plastics until recently.
Delrin.
And pretty much any brand that you find advertised in the YoYoeXpert shop area is trusted and a good brand to play around with. Anymore nobody really makes “Bad” yoyos.
It really depends on what you are looking for but I guess YYF because they make yoyos for every preferance and level. If you are just starting out or specialize in 4A I would recomend yoyojams. For experienced players and those with some money CL, SPYY, GY, and OD I can all personally recomend.
different brands specialize for different play. plz make your question more specific
edit:thanx
Preferance… 
Yes, because Duncan yoyos are for beginners only!
Totaly something you wouldn’t attempt to win worlds with lol.
But he modded it. It’s unresponsive. I bet he siliconed it.
plus, it is tyler… i think… boy has he changed.
but these are not set in stone. Duncan makes some great advanced yoyos, but they specialize in advertizing to the new player who hasn’t even heard of a double or nothing.
Duncan also has their new Screaming Eagle line. Very good yoyos.
YOYOFACTORY
Yoyofactory fits almost everybody’s preferences and makes yoyos from beginner to advanced.
In terms of looping, yoyofactory dominates with it’s loop 900.
In terms of string tricks, General yo, ILYY, SPYY, CLYW, Big brother, 3yo3, HSpin, Chico, one drop, high end YYF, Oxygen and string theory, feel free to add what i missed.
Well not necessarily, it all comes down to preference. It is a good yoyo though.