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 ZS3 and Nikon S620 side-by-side from the front, back and top in their relative dimensions. Panasonic ZS3 has external dimensions of 103 x 60 x 33 mm (4.06 x 2.36 x 1.3″) and weighs 229 g (0.50 lb / 8.08 oz) (including batteries). Nikon S620 has external dimensions of 53 x 90 x 23 mm (2.09 x 3.54 x 0.91″) and weighs 120 g (0.26 lb / 4.23 oz) (including batteries).
Below you can see the front view size comparison of Panasonic ZS3 and Nikon S620. Nikon S620 is 50mm narrower and 10mm thinner than Panasonic ZS3 but it is also 30mm taller.
Here is the back view size comparison of Panasonic ZS3 and Nikon S620.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon S620 is significantly lighter (109g ) than the Panasonic ZS3 which may become a big advantage especially on long walking trips.
Unfortunately neither Panasonic Lumix DMC-ZS3 (Lumix DMC-TZ7) nor Nikon Coolpix S620 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 Compact Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic ZS3's 3" LCD screen is slightly larger than Nikon S620's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.