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 Olympus E-M10 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). Olympus E-M10 has external dimensions of 119 x 82 x 46 mm (4.69 x 3.24 x 1.81″) and weighs 396 g (0.87 lb / 13.97 oz) (including batteries).
Below you can see the front view size comparison of Nikon S9100 and Olympus E-M10. Nikon S9100 is clearly the smaller of the two cameras. Its body is 14mm narrower, 20mm shorter and 11mm thinner than Olympus E-M10. As you can tell, actually this is not a fair size comparison since Nikon S9100 has a built-in lens but Olympus E-M10 doesn't. Once you put a lens on E-M10, its thickness will increase significantly.
Here is the back view size comparison of Nikon S9100 and Olympus E-M10.
Now lets look at the top view comparison of Nikon S9100 and Olympus E-M10.
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 (182g ) than the Olympus E-M10 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 E-M10, the total kit will weigh much higher.
Unfortunately neither Nikon Coolpix S9100 nor Olympus OM-D E-M10 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 Olympus E-M10's LCD screens has the same diagonal size of 3.00".
On the other hand, Olympus E-M10 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 E-M10.