Nikkor 28-300mm 3.5 vr VS 70-300mm 4.5 vr?

Can anyone help me with this please?

I have been searching for one week to buy a FX lense for my Nikon D7000.
SO I'm really confused between (Nikkor 28-300mm f3.5, VS 70-300mm f4.5 ).
I need a zoom lens whose pictures are sharp.
another question is:
what is the different between f3.5 and f4.5, or which one is better.

With my best regards.

Those two lenses at wide ends are quite different. At 28, for FX, it's a bit wide (but on your D7000, which is a DX format), it's not wide at all). Anyway, the other lens at the "wide end" (let us call it the shortest focal length) is at 70 mm). Think of it as your kit lens at 70 mm (almost at 85 mm).

Aperture setting of 3.5 v.s. 4.5 won't mean much - it doesn't tell you one is sharper than another. Also, these are not constant aperture lenses, I believe - so at longer end, the aperture is even smaller.

The answer is the 28-300 will be more of a walk around lens then the other one.

F3.5 is better. Why would you want an FX lens on a DX body?

I'm assuming you already have an 18-55mm and are looking for a little more reach - in which case the 70-300 is a fair option, but the 55-200 is smaller, lighter and cheaper.

The 28-300mm doesn't really give you much of a wide view on DX, and combined with size and weight is the headache designers have trying to squeeze such a massive zoom range into a single body - the 70-300 will be a far better performer.

The 28-300mm was meant as an almost-all-purpose lens for FX cameras. It is heavy and expensive. It is probably obsolete for its original purpose, as the optical deficiencies that were tolerable on the 12 MP D700 would be irksome on the 36 MP D800. If you want a superzoom for your D7000, the 18-200 or possibly the new 18-300 could be a better choice. However, if you can tolerate the lens changes, adding a 70-300mm AF-S VR to a wide-moderate zoom like the 18-55mm, 16-85mm or 18-105mm would give you better image quality.

The 28-300 mm lens is an FX lens that covers the same range on a full frame camera as the 18-200 mm covers on a DX camera like your D7000.

If you really do not know the difference between f/3.5 and f/4.5, you may not be ready to own a fully adjustable camera, at least not until you take a class in photography. This is only one of the fundamentals of photography which you need to know if you expect to produce brilliant images