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 SL3 and Canon 170 IS side-by-side from the front, back and top in their relative dimensions. Canon SL3 has external dimensions of 122 x 93 x 70 mm (4.8 x 3.66 x 2.76″) and weighs 449 g (0.99 lb / 15.84 oz) (including batteries). Canon 170 IS has external dimensions of 100 x 58 x 23 mm (3.94 x 2.28 x 0.91″) and weighs 141 g (0.31 lb / 4.97 oz) (including batteries).
Below you can see the front-view size comparison of the Canon SL3 and the Canon 170 IS. Canon 170 IS is clearly the smaller of the two cameras. Its body is 22mm narrower, 35mm shorter and 47mm thinner than Canon SL3. As you can tell, actually this is not a fair size comparison since Canon 170 IS has a built-in lens but Canon SL3 doesn't. Once you put a lens on SL3, its thickness will increase significantly.
Here is the back view size comparison of the Canon SL3 and Canon 170 IS.
Now lets look at the top view comparison of Canon SL3 and Canon 170 IS.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Canon 170 IS is significantly lighter (308g ) than the Canon SL3 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 SL3, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Canon EOS Rebel SL3 (EOS 250D / EOS Kiss X10) nor Canon PowerShot ELPH 170 IS (IXUS 170) 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 SL3's 3.00" LCD screen is slightly larger than Canon 170 IS's 2.7 screen.
Moreover, Canon SL3 sports a
Fully Articulated screen which you can change the angle and position of the screen almost freely, making it possible to shoot from waist or over-the-head levels, and especially very useful for shooting selfies and video. On the other hand, Canon 170 IS has a fixed type screen which provides almost no flexibility in shooting positions compared to SL3.