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 Panasonic G10 and Panasonic S2 side-by-side from the front, back and top in their relative dimensions. Panasonic G10 has external dimensions of 124 x 90 x 74 mm (4.88 x 3.54 x 2.91″) and weighs 388 g (0.86 lb / 13.69 oz) (including batteries). Panasonic S2 has external dimensions of 98 x 57 x 21 mm (3.86 x 2.24 x 0.83″) and weighs 112 g (0.25 lb / 3.95 oz) (including batteries).
Below you can see the front-view size comparison of the Panasonic G10 and the Panasonic S2. Panasonic S2 is clearly the smaller of the two cameras. Its body is 26mm narrower, 33mm shorter and 53mm thinner than Panasonic G10. As you can tell, actually this is not a fair size comparison since Panasonic S2 has a built-in lens but Panasonic G10 doesn't. Once you put a lens on G10, its thickness will increase significantly.
Now lets look at the top view comparison of Panasonic G10 and Panasonic S2.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Panasonic S2 is significantly lighter (276g ) than the Panasonic G10 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 G10, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Panasonic Lumix DMC-G10 nor Panasonic Lumix DMC-S2 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 Mirrorless Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic G10's 3.00" LCD screen is slightly larger than Panasonic S2's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.