although these cam are in the same class, they are very different!
Try to figure out what you will enjoy and what you may hate about these cam :
- Do you use wide angle often ? only the D7i offer you 28mm
- Max zoom : Nikon has the longest 280mm
- Do you like electric zoom ? >> go for Sony and Nikon
- Does electric buzz buzz zoom make you crazy ? ( as me) >> D7i zoom is stepless manual
- Do you like a manual focus ring ?, Nikon don't have it ( I think)
- Macro important? Check the specs
- Memory stick or Compact flash ? Sony close the door to microdrive, the 2 others ok
- Standard cheap batteries? : D7i use AA, the 2 others use proprietary . AA NiMH are sale everywhere , including walmart … , for nothing.
- Balance ? you should try all 3 in your hand for a while . Sony has the balance of a SLR with a long zoom, a point and shot guy type will hate this.
- Tilting LCD ? Only the Nikon offer you this. Very handy for auto-portrait , shoot over the crowd … more limited with the LCD in the back only.
- Burst mode important to you ? (I think that they are all ~~ 2fps)
- Nikon is black ( some like this as a "pro" look)