The Nikon S630 provides an interesting contrast to the HZ15W. It's around $50 cheaper, lacks the manual controls of the HZ15W, and has a 6x zoom lens. That said, even though it has less zoom, it has a higher telephoto range, albeit at the cost of wide-angle coverage. Also in the Nikon's favor is its generally better still image performance. It has more accurate color, significantly lower noise and less lens distortion. The Nikon also has a much nicer aesthetic, thanks to its curved design.
Of course, not everything is fantastic on the S630. It had lower image sharpness, its image stabilization didn't function as well, it couldn't get off photos as fast, and its video mode was a major letdown. The Nikon only shot video in standard definition, and lost almost all controls while in video mode, which accounts for its very low score in those sections. It also lacks the ability to manually set shutter speed and aperture when shooting stills, capabilities we find important.
If you don't need the manual controls, wide-angle lens, or HD video, the Nikon will probably serve you perfectly well, and save your wallet a bit. On the other hand, if you do want those features, go for the Samsung.