>>3587490The autofocus on the gmaster is perfect on my Rii and Riv, and the Sigma always hunted a lot more, especially in low light which is the reason I bought it in the first place. It's over 200 grams heavier which doesn't sound like a lot, but if you're walking around with it all day it does feel like a strain not only on you but on the camera if you're not supporting it properly.
Some say the Sigma is a tad sharper, but it does have a bit of copy variance because you might get a decentered lens if you're unlucky. The gmaster doesn't have this issue, and I personally like the rendering of the images on the Sony a hell of a lot more.
In the end it's what you're using it for. I do a lot of concert shoots, so I need the reliable AF speed and less overall weight. If you're doing landscapes or general street and don't mind the less than perfect autofocus then you probably won't need to pay for the premium. I personally would just rather pay for the best I can get so I don't have to worry about it later.
Having said all that, my next lens is definitely going to be Sigma's 35mm/1.2
