Have to respectfully disagree. An inferior lens manufacturer would make lenses other than what Canon offers so as to offer no apples to apples comparisons. Sigma is making (so far in their art line) superior lenses in critical flavors that go head to head with the best that Canon has...
There's only one superior lens in their art range at the moment, the 35mm f1.4. But like many Sigma lenses before, how well does it focus? The rest of Sigma's range are sub par with Canon counter parts. With Sigma, you get what you pay for.
You are terribly misinformed. The new 35mm focuses like a dream. And the USB dock has been designed to counter possible tricks by Canon in the future.
And the statement in red is plainly false.
Ok, lets qualify this a bit more. I've owned a Sigma 180 macro and used several, the AF ring was so gritty it was difficult to fine tune the focus. When compared with a Canon 180 L, there was amassive focal length difference between these two lenses. The Canon has a much longer focal length at close distances and I'm pretty sure the Sigma lost focal length as I focssed closer....not what I wanted in a Macro lens. I had a 100-300 f4 EX DG...it was pretty unspectacular in sharpness, but more seriously it's AF was pretty inaccurate, often mis focussing. It had the most stupidly huge hood...because it flared so badly in bright light. I had a 70-200 ED DG mkI, it had dreadful back focussing issues at Min Focus distance. It had AF inconsistencies, sometime accurate and sometime way off. I have a 12-24mm EX DG. A nice lens, but it's been back to Sigma twice. Once for Aperture motor burnout and a whole lens group coming loose. I had a Sigma 120-300 OS DG and to be frank it was terrible. It was sharp enough, but it was so huge. It's AF was erratic and imprecise. It was way short of the 300mm stated, closer to 280mm at infinity but down to a dissapointing 240mm at Min focus distance. When compared to my Canon 70-200 f2.8 L IS II, the small increase in Focal length wasn't worth the poor AF and massive extra bulk. None of these AF issues were related to Microfocus, the Sigma HSM motor system just isn't in the same league as the Canon USM system. I had a Sigma 24-70 (non HSM), it was a noisy AF system, but very good. The big issue was the rubbish hood and awful flare on sunny days. When I replaced it with the Canon 24-70L (mk I) it blew it away in every regard. Generally I find that Sigma lenses have a warm cast, but this varies between lens designs.
I hear from several friends who have the Sigma 50mm f1.4 and 85mm f1.4, they too get focus inconsitencies.
I don't get these issues with Canon L lenses. After the 120-300 OS DG dissapointment, I bought a 400mm f2.8 L IS which really put the Siggi in it's place. It's not just the sharpness, it's the AF's amazing accuracy.
So I'm sure you see that I have a long history with Sigma lenses in a professional basis. Most of my lenses went back to sigma and couldn't be fixed.
I'm all ears for Sigma releasing newer better lenses, but I've heared this story SO many times. I trust in Canon because they make reassuringly good kit and their prices reflect this. As I said before, and i'll restate again....the only superior lens (to Canon) in their catalogue at the moment is the 35mm f1.4. Every other lens is in some way deficient compared to it's Canon counter part.