As usual, I used the Tacmod shooting 110FPS and 600RPM full auto, and Hasbro 18 round mags from all 4 major generations. This was a zombie event, so some desperate close quarters stuff happened.
Reliability was observed as 100% with zero FTFs, zero shake'n shoots and zero gremlins in general.
By contrast, I had a mag of J-code Hasbro Elite that farked up at precisely the wrong moment and contributed to my death in the arena.
On that note, I am encountering increasing, and insidious, reliability problems with the J-code Elite Standard, even the newer stuff I observed as better. New ammo is fine. A little wear and you are guaranteed trouble - and the past few games have seen a few frantic grenade transitions because of J-code jamming, and not just from me. I am going to drop recommendation for Hasbro Standard Elite as of this post due to poor reliability and this will be reflected in the upcoming Stock Class Ammo Roundup post. If you are going to run Hasbro ammo, it's ZombieStrike Elite or buy new J-code for critical games or bust.
Back to the Yutoys koosh dart, while they ran well, they do have a quite Elitish and fragile foam, and a tacky, rubber (not PVC) tip - which is distinct from the eBay/beautifulwoman2012 sourced Koosh tips which are slicker! Thus they are not inherently a reliabuilt round like the Voberry is, and I would expect normal Elitish attrition rates with wear and normal Elitish lifespan out of these.
They also cost 2 cents per round more than Voberry, and the tip glue materials and workmanship aren't perfect either.
Now what I expect everyone wants to know, accuracy. Out of the Tacmod, they were decent. Not amazing, not the most consistent shooting ammo I have ever used, and you could get easily 10 feet of sideways spread downrange. This doesn't however seem to be a stability issue, more that these tips do not mix with inner barrels well and tend to grab and exit erratically - I was running a straight fluted inner, by the way. From a Retal they are a massive improvement over the usual short-barrel blasty wildness of elite-type darts. Meanwhile, some old scavenged and repaired BW12 kooshes (slick tip variety) are much nicer from the Tacmod (as long as you don't use a stupid rifled inner!), evidently linked to the tip situation. So that is a consideration for all you flywheelers, if you use a RS and aren't worried about .500 bore springer compatibility or eliminating tip regluing you may want to buy BW12's koosh darts rather than Yutoys. BW12's darts and their utter crap tip glue are also much easier to disassemble and clean up for proper rebonding of the tips which will give results far superior to the stock Yutoys tip glue.
ConclusionThese are perfectly serviceable, cheap, decently reliable darts with somewhat improved ballistics over the common dome tip Elite, and unlike other koosh-tip darts they are usable from the factory and compatible with stock springer barrels, but they are not perfect, nor are they the clear recommendation among all the stock class ammo I have ever used.
If I was going to buy a ton of darts tomorrow for HvZ, they would probably be Voberry's product, which may not be the cutting edge of performance and QC but does exactly what HvZ ammo needs to, which is fire every single time you pull the trigger, cost practically nothing ($16 to fill up my whole combat load worth of mags) and last practically forever compared to Elite.
For stock class? Considering that I use flywheels with inner barrels primarily, assuming BW12's koosh darts are unchanged from a few months back, I would go for BW12 koosh with reglued tips, for maximum accuracy and best ballistics with my gear.