Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Nikon S6100 and Sony A58 side-by-side from the front, back and top in their relative dimensions. Nikon S6100 has external dimensions of 98 x 58 x 27 mm (3.86 x 2.28 x 1.06″) and weighs 175 g (0.39 lb / 6.17 oz) (including batteries). Sony A58 has external dimensions of 129 x 95 x 78 mm (5.08 x 3.74 x 3.07″) and weighs 492 g (1.08 lb / 17.35 oz) (including batteries).
Below you can see the front view size comparison of Nikon S6100 and Sony A58. Nikon S6100 is clearly the smaller of the two cameras. Its body is 31mm narrower, 37mm shorter and 51mm thinner than Sony A58. As you can tell, actually this is not a fair size comparison since Nikon S6100 has a built-in lens but Sony A58 doesn't. Once you put a lens on A58, its thickness will increase significantly.
Here is the back view size comparison of Nikon S6100 and Sony A58.
Now lets look at the top view comparison of Nikon S6100 and Sony A58.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon S6100 is significantly lighter (317g ) than the Sony A58 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 A58, the total kit will weigh much higher.
Unfortunately neither Nikon Coolpix S6100 nor Sony SLT-A58 provides any type of weather sealing in their body, 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 DSLR Cameras with Weather Sealing
LCD Screen Size and Features
Nikon S6100's 3" LCD screen is slightly larger than Sony A58's 2.7" screen.
On the other hand, Sony A58 LCD screen has a Tilting feature
where you can change the angle of the screen to make it easier to shoot from waist or over the head levels. On the other hand, Nikon S6100 has a fixed type screen which provides less flexibility in shooting positions compared to A58.