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 ELPH 150 IS and Nikon D3300 side-by-side from the front, back and top in their relative dimensions. Canon ELPH 150 IS has external dimensions of 95 x 57 x 24 mm (3.74 x 2.24 x 0.94″) and weighs 142 g (0.31 lb / 5.01 oz) (including batteries). Nikon D3300 has external dimensions of 124 x 98 x 76 mm (4.88 x 3.86 x 2.99″) and weighs 430 g (0.95 lb / 15.17 oz) (including batteries).
Below you can see the front view size comparison of Canon ELPH 150 IS and Nikon D3300. Canon ELPH 150 IS is clearly the smaller of the two cameras. Its body is 29mm narrower, 41mm shorter and 52mm thinner than Nikon D3300. As you can tell, actually this is not a fair size comparison since Canon ELPH 150 IS has a built-in lens but Nikon D3300 doesn't. Once you put a lens on D3300, its thickness will increase significantly.
Here is the back view size comparison of Canon ELPH 150 IS and Nikon D3300.
Now lets look at the top view comparison of Canon ELPH 150 IS and Nikon D3300.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Canon ELPH 150 IS is significantly lighter (288g ) than the Nikon D3300 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 D3300, the total kit will weigh much higher.
Unfortunately neither Canon PowerShot ELPH 150 IS (IXUS 155) nor Nikon D3300 provides any type of weather sealing in their body, 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 Compact Cameras with Weather Sealing Top DSLR Cameras with Weather Sealing
LCD Screen Size and Features
Nikon D3300's 3.00" LCD screen is slightly larger than Canon ELPH 150 IS's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.