The biggest advantage is clearly the processing! The YN-300 II video LED is definitely different but better suited to the dimensions of her especially because of the low installation depth for use on DSLRs - the focus is better. A particularly great disadvantage of the NG-126 was extremely wobbly mount the hot shoe of the camera, the solution at the YN-300 II is here much more stable and robust for outdoor use for me.
The restriction to Sony NP-F battery is likely to have also caused a significant reduction in volume and shifts the focus more toward the center. Even with compact (replica) type batteries NP-F550, the YN-300 II video LED can theoretically operate at full luminosity - but that's not really necessary. The 300 LEDs make so much light that often 10 to 30 percent complete enough to brighten the surroundings accordingly.
The operation is very simple and easily understood instructions within minutes. On / off, brightness of the two LED groups (3,200 K, 5,500 K) Set in one or ten percent levels, battery charge - done. Since you can control very well the color temperature, the right one light taken anywhere - even without similar with the supplied filters need to handle. For me it was for example, 30 percent and 6 percent of 5,500 K 3,200 K to produce a good light for exteriors. Perfect!
Whoever has been the YN-600 Yongnuo can use the remote control of the YN-600 (three radio channels) and the YN-300 II - this needs to channel 1 are used on the remote control.
Conclusion: For the price you can not ask for more! The maximum brightness is top, the adjustable color temperatures a very nice feature and the remote control with an integrated IR remote release for Canon, Nikon and Sony a nice addition. Combined with the YN-600 incredible amount of light and quality for less money!