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 K-30 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 K-30 has external dimensions of 130 x 97 x 71 mm (5.12 x 3.82 x 2.8″) and weighs 650 g (1.43 lb / 22.93 oz) (including batteries).
Below you can see the front-view size comparison of the Nikon S9100 and the Pentax K-30. Nikon S9100 is clearly the smaller of the two cameras. Its body is 25mm narrower, 35mm shorter and 36mm thinner than Pentax K-30. As you can tell, actually this is not a fair size comparison since Nikon S9100 has a built-in lens but Pentax K-30 doesn't. Once you put a lens on K-30, its thickness will increase significantly.
Now lets look at the top view comparison of Nikon S9100 and Pentax K-30.
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 (436g ) than the Pentax K-30 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 K-30, the total kit will weigh much higher.
Weather Sealing
Thanks to the weather-sealed body of the K-30, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to the S9100.
LCD Screen Size and Features
Nikon S9100 and Pentax K-30'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.