After years with the a5000 and the classic 16-50 kit lens, I upgraded to the a6400 with the 18-135 lens.
The menu didn't seem difficult at all, as it's pretty much the same on all Sony cameras and I didn't have to learn it from scratch. Personally, I find it very simple and easy.
The custom menu also helps, as one can create their own settings, and there are also many custom external buttons that can be configured to control it even faster.
I won't go into details about the capabilities, as there are many and I would become tedious or surely miss something. There are dozens of websites and videos on YouTube that explain in detail what the camera can do and the differences it has from other models and competitors. I will only mention the main reasons why I chose this one instead of the a6500 that I initially considered:
The biggest reason is that there is no limitation on video duration. All other Sony cameras have limitations due to overheating. Some can record for 20 minutes and then shut down, others for 30 minutes. The Sony a5000 I had in the summer could record for a maximum of 35-40 minutes before shutting down due to overheating, while in winter I managed to record up to 1 hour and 15 minutes.
The a6400 has solved this major drawback, and theoretically one can record video until the memory is full or the battery runs out.
Now let's talk about the other major problem with Sony cameras, which is the battery. The a6xxx series has been using the same battery (NP-FW50) for years, which in some models (like this one) can only last for 350-400 photos or about 1 hour of video. The cherry on top is that almost all cameras in the a6xxx series do NOT support camera operation while charging. You either have to use it or charge it.
The a6400 now supports simultaneous charging, so this chronic battery problem is solved. If someone wants to shoot a 2-hour video, they can connect it to the charger or a good power bank!
This particular camera is almost the same as the a6500, but without the sensor's built-in image stabilization in the camera body, so it is considerably cheaper.
However, if someone plans to use lenses with their own built-in optical stabilization, the result is exactly the same without having to buy the much more expensive a6500!
In terms of other details, the screen is quite good, but ultimately not as bright as I expected under the sun. This is where the electronic viewfinder helps a lot, as it is much brighter than the screen and allows you to see clearly what you are aiming for, no matter how bright the day is.
Some details that bother many people who shoot videos of themselves, but not those who take photos or normal videos, is that if you connect a flash or microphone to the hot shoe and rotate the screen 180 degrees forward, the microphone obstructs the view of the screen.
Personally, it doesn't bother me at all, but for those who have such an issue, they can easily solve it by purchasing a "Hot Shoe Relocation Plate" for 10 euros and do the job.
Regarding video, the only thing I would like it to have, and I will probably miss, is a headphone output to monitor the sound in real-time.
The 18-135 lens is light years better than the standard 16-50 that Sony usually includes.
It focuses faster, has better colors, better sharpness, and is also quieter when focusing! The zoom is manual, but still quieter than the 16-50 lens, while the photos have excellent sharpness even with the aperture fully open at f/3.5! In comparison, with the 16-50 kit lens, you have to go above f/7-f/8 to start getting the same level of clarity, and that's only in the center! The 18-135, closed without zoom at 18mm, has a slight distortion (I think all zoom lenses have a little bit), but definitely smaller than the kit lens, and chromatic aberration exists but to a much lesser degree. In low light/night shots, the lens is just as dark as the basic one since both start at f/3.5, the only thing that improves things is the sensor of the a6400, which can handle high ISO without much noise, especially in videos where it can easily reach ISO 6400-8000 and have minimal noise that can be easily removed with some editing later on! I tried it with a cheap Chinese lens, the 35mm f/1.7 for 45 euros, and it was like the camera gained night vision! I know that the price difference is significant, but judging the classic standard lens 16-50 against the 18-135, I would say it's a miracle that Sony managed to market the entire a6xxx series based on such a cheap and poorly made lens! In conclusion, I would like to mention that personally, I believe that the combination of the a6400 with the 18-135 lens is one of the best combinations available, as they will cover 95% of the needs of someone who enjoys photography (or videography) but doesn't plan on buying many different lenses soon, as with this lens, they can capture wide-angle landscapes and portraits with enough bokeh, as well as distant details in landscapes or faces.