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 Canon S90 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). Canon S90 has external dimensions of 100 x 58 x 31 mm (3.94 x 2.28 x 1.22″) and weighs 195 g (0.43 lb / 6.88 oz) (including batteries).
Below you can see the front view size comparison of Canon SX20 IS and Canon S90. Canon S90 is clearly the smaller of the two cameras. Its body is 28mm narrower, 30mm shorter and 56mm thinner than Canon SX20 IS.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Canon S90 is significantly lighter (405g ) than the Canon SX20 IS which may become a big advantage especially on long walking trips.
Unfortunately neither Canon PowerShot SX20 IS nor Canon PowerShot S90 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 Compact Cameras with Weather Sealing
LCD Screen Size and Features
Canon S90's 3" LCD screen is slightly larger than Canon SX20 IS's 2.5" screen.
On the other hand, Canon SX20 IS sports a Fully Articulated screen
which you can change the angle and position of the screen almost freely, making it possible to shoot from waist or over the head levels, and especially very useful for shooting selfies and video. On the other hand, Canon S90 has a fixed type screen which provides almost no flexibility in shooting positions compared to SX20 IS.