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 S9100 and Sony NEX-3N side-by-side from the front, back and top in their relative dimensions. Nikon S9100 has external dimensions of 105 x 62 x 35 mm (4.13 x 2.44 x 1.38″) and weighs 214 g (0.47 lb / 7.55 oz) (including batteries). Sony NEX-3N has external dimensions of 110 x 62 x 35 mm (4.33 x 2.44 x 1.38″) and weighs 269 g (0.59 lb / 9.49 oz) (including batteries).
Below you can see the front view size comparison of Nikon S9100 and Sony NEX-3N. As you can tell, actually this is not a fair size comparison since Nikon S9100 has a built-in lens but Sony NEX-3N doesn't. Once you put a lens on NEX-3N, its thickness will increase significantly.
Here is the back view size comparison of Nikon S9100 and Sony NEX-3N.
Now lets look at the top view comparison of Nikon S9100 and Sony NEX-3N.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon S9100 is significantly lighter (55g ) than the Sony NEX-3N 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 NEX-3N, the total kit will weigh much higher.
Unfortunately neither Nikon Coolpix S9100 nor Sony Alpha NEX-3N 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 S9100 and Sony NEX-3N's LCD screens has the same diagonal size of 3.00".
On the other hand, Sony NEX-3N features a Tilting screen
where you can change the angle of the screen to make it easier to shoot from waist or over the head levels whereas the Nikon S9100 has a fixed type screen which provides less flexibility in shooting positions compared to NEX-3N.