I think it is suposed to be a bit better but then it depends if you need the extra reach. I had a Canon 24-105L when I had Canon cameras and it was a great focal length but I rarely used the long end [ooh er Mrs!

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I think the best all rounder is probably the 18-200mm. I have seen many great images from that lens but it's £550 new so my £82 18-70 is a real bargain plus from what i have seen it is tak sharp!
I have no experience of the 18-105mm but believe it to be good by 'kit lens' standards. However, the 18-70mm is reputed to be as near as dam-it pro standards on IQ, punching above its weight at its level in the market, as I say, thats the story and I have no reason to doubt it . . .
The 18-105mm is kit lens build quality, plastic bayonet compared with a metal bayonet fixing for instance, on the 18-70, last a long time . . .
When I made the decision to go minimalist and take on the D5000 rather than keep the D90 that I had purchased 3 months before!!! I looked at my photo files, the vast majority were in the FL of 18-70mm . . . around 35-50mm was very common.
One of the lenses I dumped was the Nikon 18-200VR mkI . . . great walkabout lens, you think . . . all that zoom, but as I say looking at picture Exifs, they regularly told a different story. Its sharp and fast focusing, but not as good as the 18-70 IMHO. It weighs 20ozs (600+grs)!!!! thats heeeeavvvvy, it does have sweet spots and 'shines', as do all zoom lenses, but, the more zoom the more the 'not so sweet spots' are noticed.
Pound for pound, less than £100 it seems, the 18-70mm is a steal . . . however, you pays your money and takes your choice. Most people are swayed by the longest zoom they can get and to hell with the picture quality, after all, its a Nikon??? . . . thats for a little while. Then reality starts to set in, can't extract that last notch of sharpness that you know can be had, colours are a bit muted and god, its heavy around the neck after walking a few miles . . . etc., etc.
All the points I make are personal and some are, may be, marginal, even of little significance to some individuals? . . . So choose carefully and wisely folks, with an open mind and both eyes open . . .
Remember, its not the camera, but the lens, and ultimately, he or she who is behind pressing the shutter that makes the picture.
CJS
PS;
So that no one is under any illusions, this is the original of the 'Hover Fly' picture posted earlier. PS is/was? needed, not much, but some. This was a JPG picture from camera. These days I would use RAW, I would expect the PS'ing to be a little better, with program RAW's greater finesse? I have added a tad of simple sharpening, a modern digital requirement and of course, the full pixel count has had to be reduced to 800 on the long edge, other wise, nothing more.