Better cameras, better pictures?

In the case of the Nikon D3, I would say yes.

• 14-bit A/D conversion and capture. More detailed color reproduction.
  
• ISO range of 200 to 6400, could be expanded to 100-25600. Great for fast action, low light situations.
  
• faster camera response and larger viewfinder.
  
• more AF points, better AF tracking.
  
• Live view. Wonderful addition. More creative options for the photographer.
  

Great camera, overall. A bit too heavy for my taste. Commentary by Thom Hogan.