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 Pentax S1 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). Pentax S1 has external dimensions of 114 x 58 x 28 mm (4.49 x 2.28 x 1.1″) and weighs 157 g (0.35 lb / 5.54 oz) (including batteries).
Below you can see the front-view size comparison of the Nikon S9100 and the Pentax S1. Pentax S1 is 4mm shorter and 7mm thinner than Nikon S9100 but it is also 9mm wider.
Here is the back view size comparison of the Nikon S9100 and Pentax S1.
Now lets look at the top view comparison of Nikon S9100 and Pentax S1.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Pentax S1 is significantly lighter (57g ) than the Nikon S9100 which may become a big advantage especially on long walking trips.
Weather Sealing
Unfortunately neither the Nikon Coolpix S9100 nor Pentax Optio S1 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
LCD Screen Size and Features
Nikon S9100's 3.00" LCD screen is slightly larger than Pentax S1's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.