"The extra 2mm" doesn't sound like much, but its quite a bit, when you look at focal length comparisons of the field of view. Is it worth the size, weight and cost? Only you can decide. Another thing to think about, though, is the long end and what you might be likely to use that for. With the 7-14, the long end is still pretty wide. On the 9-18, the long end comes right into fairly common prime territory (ie, right between the 17 and the 20). I've found myself using the 18 for a fair amount of the same kind of street shooting I'd use the 17 or 20 for, as long as it wasn't REALLY low light. Here are a couple that weren't taken with all that much light, but enough (not great shots - wouldn't show them for content, but as a lens demo, what the heck....).
For me, the long end was a big part of what made the 9-18 a no brainer. Size and weight were real factors too. And the money, but if I'd REALLY wanted the 7-14, I'd have found a way to rationalize the difference.
-Ray
<a href="http://www.flickr.com/photos/20889767@N05/4686956728/" title="R-5 by ramboorider1, on Flickr">
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<a href="http://www.flickr.com/photos/20889767@N05/4686956794/" title="Broad St Line by ramboorider1, on Flickr">
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