Received the KZ-Vader Balanced version today. I purchased it with my own money, mainly because it looks prettier (so why not, haha). TLDR: the force is strong with Vader Balance version.
The most popular question: Do they sound similar to the Trio?
Comparison is based on 1111 setting from both.
I will say, they share the same tuning. However, the mid-bass is less elevated in the Vader. The upper-mid/ultra-treble in the Vader is just better, with a very similar vibe to the ZS10 Pro 2 but more resolving and less harsh. In fact, with some tracks that already have bass boosted, you will find the bass on Trio is slightly bloated and the vocal is a bit thin, while Vader does this perfectly. This track is an example:
YOASOBI "Racing into the Night". It really depends on your collection, if you are fine with Trio, don't bother to buy Vader.
The Vader is also harder to drive, you need around 20% more power to achieve the same sound pressure.
In terms of dimensions, they are just the same, but the Vader's faceplate makes them more eye-pleasing. The internal board is similar too, but the wiring on the Vader is thicker and looks more muscular.
Overall, I think Vader is an upgrade over Trio, though the improvements are just minor.