Generally, some of the advantages of the Sigma SD15 compared to other entry-level DSLR competitors include: it has a slightly larger screen (3" vs 2.5"), has higher quality type of viewfinder (pentaprism vs pentamirror) and has a CMOS-family sensor (CMOS vs CCD).
However, on average it doesn't record movies (none vs 1080p @ 24fps), has a much lower resolution screen (150k dots vs 920k dots), significantly smaller viewfinder (0.52x vs 0.61x), doesn't have image stabilization (none vs sensor shift) and takes much lower resolution photos (4.6 MP vs 16.1 MP).
Nikon D5100
2 years newer
$372 (body only)
Significant advantages of the D5100 (vs the SD15)
- Much higher true resolution: 16.1 MP vs 4.6 MP
- Much higher resolution screen: 920k dots vs 150k dots
- Has live view
Significant disadvantages of the D5100 (vs the SD15)
- Doesn't have a pentaprism viewfinder: Pentamirror vs Pentaprism
- Less viewfinder coverage: 95% vs 98%
common strengths of the D5100 and SD15
- Both use faster phase detection autofocus: Phase detection vs Phase detection
Nikon D80
2 years older
$266 (body only)
Significant advantages of the D80 (vs the SD15)
- Much higher true resolution: 10 MP vs 4.6 MP
- Much larger viewfinder: 0.62x vs 0.52x
- Much more lenses available: 230 lenses vs 37 lenses
Significant disadvantages of the D80 (vs the SD15)
- Much smaller screen: 2.5" vs 3"
- Has a CCD-family sensor: CCD vs CMOS
- Less viewfinder coverage: 95% vs 98%
common strengths of the D80 and SD15
- Both have pentaprism viewfinders: Pentaprism vs Pentaprism
- Both use faster phase detection autofocus: Phase detection vs Phase detection
Nikon D7000
2 years newer
$602 (body only)
Significant advantages of the D7000 (vs the SD15)
- Much higher true resolution: 16.1 MP vs 4.6 MP
- Much higher resolution screen: 920k dots vs 150k dots
- Has live view
Significant disadvantages of the D7000 (vs the SD15)
common strengths of the D7000 and SD15
- Both have pentaprism viewfinders: Pentaprism vs Pentaprism
- Both use faster phase detection autofocus: Phase detection vs Phase detection
Pentax K-500
4 years newer
Significant advantages of the K-500 (vs the SD15)
- Much higher true resolution: 16.1 MP vs 4.6 MP
- Much higher resolution screen: 921k dots vs 150k dots
- Image stabilization:
- Sensor shift
vs None
Significant disadvantages of the K-500 (vs the SD15)
common strengths of the K-500 and SD15
- Both have pentaprism viewfinders: Pentaprism vs Pentaprism
- Both use faster phase detection autofocus: Phase detection vs Phase detection
Canon Rebel T4i
3 years newer
Significant advantages of the T4i (vs the SD15)
- Much higher true resolution: 17.9 MP vs 4.6 MP
- Much higher resolution screen: 1,040k dots vs 150k dots
- Has live view
Significant disadvantages of the T4i (vs the SD15)
- Doesn't have a pentaprism viewfinder: Pentamirror vs Pentaprism
- Less viewfinder coverage: 95% vs 98%
common strengths of the T4i and SD15
- Both use faster phase detection autofocus: Phase detection vs Phase detection