I am in a bit of a thought process at the moment and getting nowhere fast, can you help me please?

I have recently got myself a Nikon D5000, I have with it an 18-55 kit lens but I would like to reach further. I have been looking at zoom lenses and have narrowed it down to two,

Number 1 is the Tamron 18-270mm f3.5-6.3 Di II VC Lens for Nikon AFS.

Number 2, is The AF-S VR Zoom-Nikkor 70-300mm f/4.5-5.6G IF-ED.

My thoughtts at present is to go with the Nikon as I already have an 18-55 which has the wide angle side of things covered, well wide enough for me at present. I just don't know which lens would be best.

Ny thoughts, experiences appreciated