Which zoom lens out of the two?

I have a Nikon D3000 and am looking to get a zoom lens, I have had my eye on getting the Sigma 70-300mm f4-5.6 DG OS lens for awhile but also saw the Tamron 70-300mm f4-5.6 Di with AF Motor, the Tamron is more than £100 cheaper, but just wondering does it pay to cash out more than £100 for the Sigma or will the Tamron give me good enough results? I'm interested in wildlife, landscape and cityscape photography incase that helps and my experience is beginner.

Thanks

Added (1). I have decided to get the Sigma 70-300mm f/4.5-5.6 APO DG Macro, thanks for your reply though.

If you are just a beginner, then I do not see much reason in spending 100 pounds more money on a lens which is basically the same.
So go the Tamron, unless you want a lens that is more of an investment to last your for your lifetime (?!) I would still say the Tamron.

Also - I question using this lens for cityscape and landscape, it would be better to buy a nice wideangle lens, wouldnt it? Something like a 10-24mm, because at 70mm you won't get those stunning wide angle cityscapes?!