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 Olympus E-620 and Casio EX-100 side-by-side from the front, back and top in their relative dimensions. Olympus E-620 has external dimensions of 130 x 94 x 60 mm (5.12 x 3.7 x 2.36″) and weighs 500 g (1.10 lb / 17.64 oz) (including batteries). Casio EX-100 has external dimensions of 119x67x50 mm and weighs 389 g (including batteries).
Below you can see the front-view size comparison of the Olympus E-620 and the Casio EX-100. Casio EX-100 is clearly the smaller of the two cameras. Its body is 11mm narrower, 27mm shorter and 10mm thinner than Olympus E-620. As you can tell, actually this is not a fair size comparison since Casio EX-100 has a built-in lens but Olympus E-620 doesn't. Once you put a lens on E-620, its thickness will increase significantly.
Here is the back view size comparison of the Olympus E-620 and Casio EX-100.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Casio EX-100 is significantly lighter (111g ) than the Olympus E-620 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 E-620, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Olympus E-620 nor Casio Exilim EX-100 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 DSLR Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Casio EX-100's 3.50" LCD screen is slightly larger than Olympus E-620's 2.7" screen.