Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Canon 400D and Canon D10 side-by-side from the front, back and top in their relative dimensions. Canon 400D has external dimensions of 127 x 94 x 65 mm (5 x 3.7 x 2.56″) and weighs 556 g (1.23 lb / 19.61 oz) (including batteries). Canon D10 has external dimensions of 104 x 67 x 49 mm (4.09 x 2.64 x 1.93″) and weighs 190 g (0.42 lb / 6.70 oz) (including batteries).
Below you can see the front view size comparison of Canon 400D and Canon D10. Canon D10 is clearly the smaller of the two cameras. Its body is 23mm narrower, 27mm shorter and 16mm thinner than Canon 400D. As you can tell, actually this is not a fair size comparison since Canon D10 has a built-in lens but Canon 400D doesn't. Once you put a lens on 400D, its thickness will increase significantly.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Canon D10 is significantly lighter (366g ) than the Canon 400D 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 400D, the total kit will weigh much higher.
Thanks to the weather sealed body of D10, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to 400D.
LCD Screen Size and Features
Canon 400D and Canon D10's LCD screens has the same diagonal size of 2.5".
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.