I have used G&G, Goldenball, TSD, KSC, Javelin, Echo 1, PHX, Airsoft Elite, and AirSplat house brand.
The Javelins were awful. Stay Away.
I was very hit-or-miss (no pun intended) with Echo 1. Some bags were pretty good, others weren't so good.
PHX, G&G, Airsoft Elite, Goldenball and KSC were all very high quality and extremely consistent. I would recommend them highly.
Airsplat and TSD are okay bb's. No problems, just a little less consistent than the others.
Lots of other people with lots of other experiences. These are my opinions. Based on real life testing. Very little of this testing was done in a controlled environment, and most of this is only opinion and may be errant due to the many other factors. lol.