Which lens is better?

Http://www.jessops.com/online.store/products/78033/show.html
OR
http://www.jessops.com/online.store/products/77949/show.html

On amazon the nikon is £255 and the Tamron is £307, but what is making the tamron so much more expensive, as they both seem the same to me? Are there any differences?

The Tamron is f/4 at 70mm whereas the Nikon is f/4.5 at 55mm which makes the Nikon a slower lens at the shorter end of the zoom. You pay for faster lenses, that's why a 300mm f/2.8 lens is nearly £4000. The Tamron is likely to be a marginally better lens optically.

Tamron is a more modern design. It uses an internal focusing setup, which makes it much faster to focus, allows the easy use of a polarising filter and you can manually focus the lens without switching the lens from AF to MF.

Additionally the Nikkor is a low quality lens aimed at consumers, whilst the Tamron is from it's SP series which is a premium lens aimed at more serious users.

Edit - NB. Tamron also make a non-SP version of the lens, which is the Tamron 70-300mm f4-5.6Di LD Macro (the model code is A17), and is not a real macro lens. This lens is rubbish.

Here are links to in-depth reviews, including image quality tests for these two lenses:

http://www.slrgear.com/...39/cat/all

http://www.slrgear.com/...59/cat/all

Both lenses have fast, quiet autofocus. The Tamron lens is overall more sharp, but exhibits more CA (chromatic aberation, aka color fringing). Users complain of the Nikon lens as being very soft at the 300mm end. The IQ tests confirm this.

If I were you, I'd get the Nikon 70-300mm f/4.5-5.6G ED IF AF-S VR instead. Yes, it's about £100 more, but much better in all regards than the other two zooms. Well worth it.

Happy shopping