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 Canon 4000D and Canon A3400 IS side-by-side from the front, back and top in their relative dimensions. Canon 4000D has external dimensions of 129 x 102 x 77 mm (5.08 x 4.02 x 3.03″) and weighs 436 g (0.96 lb / 15.38 oz) (including batteries). Canon A3400 IS has external dimensions of 94 x 56 x 21 mm (3.7 x 2.2 x 0.83″) and weighs 126 g (0.28 lb / 4.44 oz) (including batteries).
Below you can see the front-view size comparison of the Canon 4000D and the Canon A3400 IS. Canon A3400 IS is clearly the smaller of the two cameras. Its body is 35mm narrower, 46mm shorter and 56mm thinner than Canon 4000D. As you can tell, actually this is not a fair size comparison since Canon A3400 IS has a built-in lens but Canon 4000D doesn't. Once you put a lens on 4000D, its thickness will increase significantly.
Here is the back view size comparison of the Canon 4000D and Canon A3400 IS.
Now lets look at the top view comparison of Canon 4000D and Canon A3400 IS.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Canon A3400 IS is significantly lighter (310g ) than the Canon 4000D 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 4000D, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Canon EOS 4000D nor Canon PowerShot A3400 IS provides any type of weather sealing in their bodies, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top DSLR Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Canon A3400 IS's 3.00" LCD screen is slightly larger than Canon 4000D's 2.7 screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.