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-PM2 and Canon SD3500 IS side-by-side from the front, back and top in their relative dimensions. Olympus E-PM2 has external dimensions of 110 x 64 x 34 mm (4.33 x 2.52 x 1.34″) and weighs 269 g (0.59 lb / 9.49 oz) (including batteries). Canon SD3500 IS has external dimensions of 99 x 56 x 22 mm (3.9 x 2.2 x 0.87″) and weighs 160 g (0.35 lb / 5.64 oz) (including batteries).
Below you can see the front-view size comparison of the Olympus E-PM2 and the Canon SD3500 IS. Canon SD3500 IS is clearly the smaller of the two cameras. Its body is 11mm narrower, 8mm shorter and 12mm thinner than Olympus E-PM2. As you can tell, actually this is not a fair size comparison since Canon SD3500 IS has a built-in lens but Olympus E-PM2 doesn't. Once you put a lens on E-PM2, 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.
Canon SD3500 IS is significantly lighter (109g ) than the Olympus E-PM2 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-PM2, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Olympus PEN E-PM2 nor Canon PowerShot SD3500 IS / IXUS 210 / IXY 10S 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 Mirrorless Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Canon SD3500 IS's 3.50" LCD screen is slightly larger than Olympus E-PM2's 3" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.