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 Panasonic GH2 and Canon SX30 IS side-by-side from the front, back and top in their relative dimensions. Panasonic GH2 has external dimensions of 124 x 90 x 76 mm (4.88 x 3.54 x 2.99″) and weighs 442 g (0.97 lb / 15.59 oz) (including batteries). Canon SX30 IS has external dimensions of 123 x 92 x 108 mm (4.84 x 3.62 x 4.25″) and weighs 601 g (1.32 lb / 21.20 oz) (including batteries).
Below you can see the front view size comparison of Panasonic GH2 and Canon SX30 IS. Panasonic GH2 is 2mm shorter and 32mm thinner than Canon SX30 IS but it is also 1mm wider. As you can tell, actually this is not a fair size comparison since Canon SX30 IS has a built-in lens but Panasonic GH2 doesn't. Once you put a lens on GH2, 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.
Panasonic GH2 is significantly lighter (159g ) than the Canon SX30 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 GH2, the total kit will weigh much higher.
Unfortunately neither Panasonic Lumix DMC-GH2 nor Canon PowerShot SX30 IS 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 Mirrorless Cameras with Weather Sealing Top Bridge Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic GH2's 3" LCD screen is slightly larger than Canon SX30 IS's 2.7" screen.