Size and weight are big decision factors when you are trying to find the ideal camera for your needs.
In this section, we are going to illustrate the Sony A6400 and Sony QX100 side-by-side from the front, back and top in their relative dimensions. Sony A6400 has external dimensions of 120 x 67 x 60 mm (4.72 x 2.64 x 2.36″) and weighs 403 g (0.89 lb / 14.22 oz) (including batteries). Sony QX100 has external dimensions of 63 x 63 x 56 mm (2.46 x 2.46 x 2.19″) and weighs 179 g (0.39 lb / 6.31 oz) (including batteries).
Below you can see the front-view size comparison of the Sony A6400 and the Sony QX100. Sony QX100 is clearly the smaller of the two cameras. Its body is 57mm narrower, 4mm shorter and 4mm thinner than Sony A6400. As you can tell, actually this is not a fair size comparison since Sony QX100 has a built-in lens but Sony A6400 doesn't. Once you put a lens on A6400, its thickness will increase significantly.
Now lets look at the top view comparison of Sony A6400 and Sony QX100.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Sony QX100 is significantly lighter (224g ) than the Sony A6400 which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on A6400, the total kit will weigh much higher.
Weather Sealing
With its weather-sealed body, we believe that the A6400 has a big advantage over the QX100 which doesn't provide any kind of environmental sealing.
LCD Screen Size and Features
Sony A6400's 3.00" LCD screen is slightly larger than Sony QX100's screen.
In addition to the size advantage, Sony A6400 LCD screen also has a
Tilting feature where you can change the angle of the screen to make it easier to shoot from waist or over-the-head levels. On the other hand, Sony QX100 has a fixed type screen which provides less flexibility in shooting positions compared to A6400.