If you're looking to do urban street shots and landscapes, you're actually not going to benefit from either of those lens. You want versatility. For your scope, you need something fairly wide for landscapes to normal perspective for urban shooting. The 18-200 lens is probably the best lens as far as versatility goes.
What to look for when buying lens:
1. consider your price cap - lens get expensive...quickly
2. after realizing your price cap, consider your application - shooting landscapes usually means you want wide (16-35mm range), shooting people usually means you want more normal (35-85mm range), and wildlife/event photography means telephoto (70-600mm range). Of course, rules can always be broken when necessary, but not always practically
3. when you've decided which lens range you want, look at the fastest speed. f/2.8 or lower is considered fast. faster = less blur in darker settings such as indoors/evening when shooting without a flash. Typically, any zoom lens at 2.8 tends to get pretty pricey. Since you're a Nikon shooter, you don't have many primes to select from. Primes usually start at about 2.0 and lower. They're mega fast lens, but you lose your ability to zoom. That's what feet are for
4. buy that lens after you've found the fastest, most applicable lens you can afford
In photography, lens is an investment. Unlike your camera, your lens value will be worth almost the same 10 yrs from now depending on the condition of the lens and how good it is. If it's a crappy lens, it's not worth much later, but a pro lens does not depreciate much at all.