While I'm no expert on Nikon lenses (Canon user here). If the same holds true for Nikon then both have their pro's and cons.
One lens:
Pros;
Less lens changing (less sensor dust)
Greater range of focal distances for quick shots (not being stuck with 'wrong' size lens for situation)
Cons:
Heavier/bulkier
May have a lesser quality glass if cheaper (in Canon there is a 'professional' grade glass that does cover that range and it's VERY expensive but quality is noticably sharper)
Smaller F stops (meaning not very good for low light F/5.6 and up)
Harder to hand hold shots (may need tripod more often for many shots including low light)
Two lenses:
Pros:
Lighter weight no matter which lens you have on
Higher quality glass (depends on specifics see above note)
Wider F stops (better for lower light pictures or bokeh F/4.0 and under)
Cons:
More often lens changes (greater chance of sensor dust, may also have on 'wrong' lens for shot)
More to carry with you on a photo shoot (although any photography gear nut may have at least 70 lbs of weight in a backpack at any given time)
Like I said I'm not all that familiar with Nikon specifics, however in general there shouldn't be too many differences from Canon.
In general it can be said of ANY camera manufacturer that the kit lenses STINK in quality.
Hope your dream camera and you have many happy hours of shooting.
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