I'm about to buy a Nikon D3100 and can't decide which kit lens I should pick. On the one hand there is the standard AF-S 18-55mm VR lens and on the other hand the AF-S 18-105mm VR. A bit more zoom than the 55mm lens would be nice, but is the 18-105mm lens as quite as good as the 18-55mm at the same focal-lengths or do I have much more distortion and quality loss in wide angle?
Both of these lenses are plenty good enough; sure, there are differences, but particularly as a beginner, you won't notice them.
I would recommend the 18-105 because the flexibility of a bit more length is of great value to beginners, because it helps you figure out what focal lengths you prefer.
I bought the 18-105 with my D90, and in retrospect, I wish I hadn't.
I got the 50mm f1.8 soon after, and the image quality is leaps and bounds above the 18-105. So now, whenever I am taking something serious (portraits, etc), I use it.
I then got the 35mm f2, which gives me a wider angle with better image quality. Now, whenever I need a wider angle than the 50, I use it.
I find myself not doing much at all at the 105mm end of the lens. It's not really long enough for most times when you really want a zoom.
As such: it now barely gets any use. And so I wish I spent the money on other stuff.
The 18-55 seems to be a really good focal length range; for "real zooming" I'd want something longer. In retrospect, I wish I'd gotten this lens instead... or simply gone without a kit lens entirely and gotten the 50 & the 35.
Maybe you want to have a look here: http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/234-nikkor-af-s-18-55mm-f35-56-g-ed-dx-ii-review--test-report For the 18-55 but without VR (Don't know if the VR is much different to this one)
and here: http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/410-nikkor_18105_3556vr For the 18-200.
This should give you a good overview!
The quality of the optics on those two lens is fairly comparable and since, to my knowledge as a D3100 owner, you can't get a body only and a different lens - then get the longer focal length only if you think you need it. Otherwise, take the price difference and put it towards something that will produce a better picture for the kinds of shots you'll be doing. DSLRs are MUCH more fun when you have a better lens than the kit to play with.
If you're going to be doing portrait, look at something like a 50mm 1.4 or a SB-600 flash.
If you're going to be shooting indoors, but mostly "scene captures" or such - the 35mm 1.8 is VERY reasonably priced.
If you're going to be shooting landscape - a decent tripod, set of filters, or if you can spring for the 10-24mm lens.