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 Pentax RZ18 and Olympus E-PL1 side-by-side from the front, back and top in their relative dimensions. Pentax RZ18 has external dimensions of 97 x 61 x 33 mm (3.82 x 2.4 x 1.3″) and weighs 178 g (0.39 lb / 6.28 oz) (including batteries). Olympus E-PL1 has external dimensions of 115 x 72 x 42 mm (4.53 x 2.83 x 1.65″) and weighs 334 g (0.74 lb / 11.78 oz) (including batteries).
Below you can see the front-view size comparison of the Pentax RZ18 and the Olympus E-PL1. Pentax RZ18 is clearly the smaller of the two cameras. Its body is 18mm narrower, 11mm shorter and 9mm thinner than Olympus E-PL1. As you can tell, actually this is not a fair size comparison since Pentax RZ18 has a built-in lens but Olympus E-PL1 doesn't. Once you put a lens on E-PL1, its thickness will increase significantly.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Pentax RZ18 is significantly lighter (156g ) than the Olympus E-PL1 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-PL1, the total kit will weigh much higher.
Weather Sealing
With its weather-sealed body, we believe that the RZ18 has a big advantage over the E-PL1 which doesn't provide any kind of environmental sealing.
LCD Screen Size and Features
Pentax RZ18's 3.00" LCD screen is slightly larger than Olympus E-PL1's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.