Which lens is better for Nikon D90? - 1

I'm using 18-105mm on my Nikon D90 and i'm looking for zoom lens. I'm really tight on budget. I have shortlisted two lens

Sigma 70-300mm F4-5.6 APO DG Macro (Motorized for Nikon Digital SLR) Lens

Tamron AF 70-300mm F/4-5.6 Di LD Macro (for Nikon Digital SLR) Lens

Or should i wait and then go for some other lens. If yes then do suggest that option also.

Save your money and buy a Nikon lens.

The 55-200mm is not that expensive, and in reality, there's not a lot of difference between 200 and 300mm.

What you don't understand is that it's not about the lens to camera, it's about you knowing how to use the lens. Of course Nikon will give you the best lenses for your camera but what's best for you? Well you'll have to decide that based on your lens skills and what you intend to shoot.

If you really need a tele-zoom right now search for tamron 70-300 or nikon 55-200VR

obviously 55-300VR - 70-300VR and tamron 70-300VC - 70-200/2, 8 are better [ and more expensive ] options ;-)