Unfortunately those 3 brands you listed have never tested at their advertised specs, when we tested them, however out of the 3 the Bluebird was simply terrible, The Bluebird averaged only half of what they advertise, supposed to produce 47kg at 7.4v, yet didn't even hit 40kg, and only averaged 25kg. Let's just say after I did my demonstration at our local track, the guys that used to recommend them, and run them didn't do so anymore. As I always say, the results speak for themselves. I always like to add, our torque tester is pretty industry standard, however if these companies have some sort of magic torque tester, and they produce the advertised torque they state, then imagine what our servos would produce on that same machine if ours are already more powerful than the brands we have tested on our equipment.

Bluebird Brushless Servo Torque Test model BLS-M45B. By the way, this servo failed in less than 2 weeks, and the one I tested was the new one they gave me only after I waited almost 2 months for a replacement from them. I literally had to jump thru hoops to get them to replace it, and had to have local guys at my track vouch that it was installed correctly, and since it was an intermittent issue I had to drive my car till it started to act up and get it on video as well which caused unnecessary damage to my car as I could not get it to act up on the bench. Even with a rubber band it would not return to neutral, so basically the car would get stuck at a certain throttle position, and my car would go running wild. Only till I caught the issue on video they would replace it, even though I had purchased it less than 2 weeks before it acting up. I have a ton more videos of various servos models, and I will post them up in our channel, as I don't want to just upload everything all at once.

https://www.youtube.com/watch?v=uQdoppOqeNU