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 Sony G3 and Panasonic GF2 side-by-side from the front, back and top in their relative dimensions. Sony G3 has external dimensions of 97 x 59 x 22 mm (3.82 x 2.32 x 0.87″) and weighs 185 g (0.41 lb / 6.53 oz) (including batteries). Panasonic GF2 has external dimensions of 113 x 68 x 33 mm (4.45 x 2.68 x 1.3″) and weighs 310 g (0.68 lb / 10.93 oz) (including batteries).
Below you can see the front-view size comparison of the Sony G3 and the Panasonic GF2. Sony G3 is clearly the smaller of the two cameras. Its body is 16mm narrower, 9mm shorter and 11mm thinner than Panasonic GF2. As you can tell, actually this is not a fair size comparison since Sony G3 has a built-in lens but Panasonic GF2 doesn't. Once you put a lens on GF2, its thickness will increase significantly.
Here is the back view size comparison of the Sony G3 and Panasonic GF2.
Now lets look at the top view comparison of Sony G3 and Panasonic GF2.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Sony G3 is significantly lighter (125g ) than the Panasonic GF2 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 GF2, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Sony Cyber-shot DSC-G3 nor Panasonic Lumix DMC-GF2 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
Sony G3's 3.50" LCD screen is slightly larger than Panasonic GF2's 3" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.