Generally, some of the advantages of the Canon S30 compared to compact competitors include: it has a much larger screen (1.8" vs 1.5").
However, on average it is much larger (mid size (112×58×42 mm) vs compact (87×57×28 mm)), is older (october 2001 vs february 2003), is thicker (1.7" vs 1.1"), is much heavier (323 g vs 230 g) and has a slower max shutter speed (1/1500 of a second vs 1/2000 of a second).
Canon PowerShot S400
1 year newer
Significant advantages of the S400 (vs the S30)
- Much smaller: Compact (87×57×28 mm) vs Mid size (112×58×42 mm)
- Much thinner: 1.1" vs 1.7"
- Much lighter: 230 g vs 323 g
Significant disadvantages of the S400 (vs the S30)
- Much smaller screen: 1.5" vs 1.8"
common strengths of the S400 and S30
- Wide aperture: f/2.8 vs f/2.8
- Both have tunnel viewfinders: Tunnel vs Tunnel