About the Tamron Lens?

Right now i wanna buy Tamron Telephoto zooms: 70 - 300mm Lens but i don't know that lens is good or bad? Or Canon and Nikon better? Can anyone give me about the result

http://www.tamron.ca/product.htm?Product=104A005E&Source=Category&Category=TAM_TELEZOOM_E

Added (1). And about this one? Http://www.futureshop.ca/en-CA/product/canon-canon-ef-70-300mm-f-4-0-5-6is-usm-lens-0345b002/10079240.aspx?path=8e2421f326b32cd1e5cd4bb0e8001693en02

good best?

I have an older version of the Tamron 70-300 f/4-5.6.It is not a great lens, but it does OK for the stuff I use it for, mainly daytime Little League baseball games at middle aperture. The af is prone to hunt, especially in low light, (which for this lens means in the shade.) It is simply not sharp at wide aperture or at either end of the focal range. It's best redeeming quality is it is cheap. I would guess that no consumer 70-300 lenses have stellar image quality, but in general the OEM versions of most lenses are a little better than the third party versions.

Here is a picture from my Flickr using that lens last weekend. I uploaded a larger file than I usually do for Flickr, so you can inspect it closer. The exif data is intact, if you want to see, I think it is ISO 320, 1/500 @ f/11.

If you are on a budget, it is an OK lens, providing you don't need low light or maximum sharpness. It would not be a very good bird or wedding lens, for instance. For the price, not too bad, but you get what you pay for!