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 Canon SX20 IS and Sony NEX-5 side-by-side from the front, back and top in their relative dimensions. Canon SX20 IS has external dimensions of 128 x 88 x 87 mm (5.04 x 3.46 x 3.43″) and weighs 600 g (1.32 lb / 21.16 oz) (including batteries). Sony NEX-5 has external dimensions of 111 x 59 x 38 mm (4.37 x 2.32 x 1.5″) and weighs 287 g (0.63 lb / 10.12 oz) (including batteries).
Below you can see the front view size comparison of Canon SX20 IS and Sony NEX-5. Sony NEX-5 is clearly the smaller of the two cameras. Its body is 17mm narrower, 29mm shorter and 49mm thinner than Canon SX20 IS. As you can tell, actually this is not a fair size comparison since Canon SX20 IS has a built-in lens but Sony NEX-5 doesn't. Once you put a lens on NEX-5, 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.
Sony NEX-5 is significantly lighter (313g ) than the Canon SX20 IS 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 NEX-5, the total kit will weigh much higher.
Unfortunately neither Canon PowerShot SX20 IS nor Sony Alpha NEX-5 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 Bridge Cameras with Weather Sealing Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Sony NEX-5's 3" LCD screen is slightly larger than Canon SX20 IS's 2.5" screen.