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 Nikon S9100 and Panasonic GM1 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). Panasonic GM1 has external dimensions of 99 x 55 x 30 mm (3.88 x 2.16 x 1.2″) and weighs 204 g (0.45 lb / 7.20 oz) (including batteries).
Below you can see the front-view size comparison of the Nikon S9100 and the Panasonic GM1. Panasonic GM1 is clearly the smaller of the two cameras. Its body is 6mm narrower, 7mm shorter and 5mm thinner than Nikon S9100. As you can tell, actually this is not a fair size comparison since Nikon S9100 has a built-in lens but Panasonic GM1 doesn't. Once you put a lens on GM1, its thickness will increase significantly.
Here is the back view size comparison of the Nikon S9100 and Panasonic GM1.
Now lets look at the top view comparison of Nikon S9100 and Panasonic GM1.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Panasonic GM1 is 10g lighter than the Nikon S9100 but we don't think this will make a significant difference.
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 GM1, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Nikon Coolpix S9100 nor Panasonic Lumix DMC-GM1 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 Compact Cameras with Weather Sealing Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Nikon S9100 and Panasonic GM1's LCD screens have the same diagonal size of 3.00 inches.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.