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 D3 and Pentax XG-1 side-by-side from the front, back and top in their relative dimensions. Nikon D3 has external dimensions of 160 x 157 x 88 mm (6.3 x 6.18 x 3.46″) and weighs 1300 g (2.87 lb / 45.86 oz) (including batteries). Pentax XG-1 has external dimensions of 119 x 89 x 98 mm (4.69 x 3.5 x 3.84″) and weighs 567 g (1.25 lb / 20.00 oz) (including batteries).
Below you can see the front-view size comparison of the Nikon D3 and the Pentax XG-1. Pentax XG-1 is 41mm narrower and 68mm shorter than Nikon D3 but it is also 10mm thicker. As you can tell, actually this is not a fair size comparison since Pentax XG-1 has a built-in lens but Nikon D3 doesn't. Once you put a lens on D3, its thickness will increase significantly.
Here is the back view size comparison of the Nikon D3 and Pentax XG-1.
Now lets look at the top view comparison of Nikon D3 and Pentax XG-1.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Pentax XG-1 is significantly lighter (733g ) than the Nikon D3 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 D3, the total kit will weigh much higher.
Weather Sealing
With its weather-sealed body, we believe that the D3 has a big advantage over the XG-1 which doesn't provide any kind of environmental sealing.
LCD Screen Size and Features
Nikon D3 and Pentax XG-1'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.