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.