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 Nikon L120 and Nikon 1 J3 side-by-side from the front, back and top in their relative dimensions. Nikon L120 has external dimensions of 110 x 77 x 78 mm (4.33 x 3.03 x 3.07″) and weighs 431 g (0.95 lb / 15.20 oz) (including batteries). Nikon 1 J3 has external dimensions of 101 x 61 x 29 mm (3.98 x 2.4 x 1.14″) and weighs 201 g (0.44 lb / 7.09 oz) (including batteries).
Below you can see the front view size comparison of Nikon L120 and Nikon 1 J3. Nikon 1 J3 is clearly the smaller of the two cameras. Its body is 9mm narrower, 16mm shorter and 49mm thinner than Nikon L120. As you can tell, actually this is not a fair size comparison since Nikon L120 has a built-in lens but Nikon 1 J3 doesn't. Once you put a lens on 1 J3, its thickness will increase significantly.
Comparison image of Nikon L120 and Nikon 1 J3 Size, Weight and External Dimensions - Front View
Now lets look at the top view comparison of Nikon L120 and Nikon 1 J3.
Top View Comparison image of Nikon L120 and Nikon 1 J3 Size
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon 1 J3 is significantly lighter (230g ) than the Nikon L120 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 1 J3, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither Nikon Coolpix L120 nor Nikon 1 J3 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 Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Nikon L120 and Nikon 1 J3's LCD screens has the same diagonal size of 3".
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.