Tamron SP AF 10-24mm F/3.5-4.5 (VS) Sigma 10-20mm F/4-5.6?

I want to buy a wide angel lens for my Nikon D3100, kindly suggest me which one is batter, Tamron SP AF 10-24mm F/3.5-4.5
VS
Sigma 10-20mm F/4-5.6

I own one Tamron lens that has focus and aberration issues so I don't recommend the brand. I have a good friend who owns a Sigma and has great luck with it.

There's nothing wrong with Tamron in general, they make excellent standard zoom lenses (e.g. The 17-50mm/2.8). Never judge a brand by a single bad lens. Even Nikon and Canon have the occasional bad lens.

Either way, i'd prefer the Sigma lens. It has a very good reputation, and generally better reviews than the Tamron counterpart.