Can you compare Sigma 12-24 and Tokina 11-16 on a crop ?

I shoot Sony mirrorless but I assume optically Canon versions are the same.

I currently have the first gen Sigma, a sharp copy. I am pretty happy with it except for size, weight and being too slow to use on the inside without a flash.

Looking at Tokina, it is faster at f2.8 so I assume by f4.5 it should beat Sigma. It's also smaller and lighter, even if not by much. It's 1mm wider, even though I lose 8 mm on the other end. However it seems every mm gained on the wid end is a much more spectacular difference.

So, if you had a chance to use both, can you comment on the IQ and other factors ? From what I read, Tokina may not have the most accurate AF.

I disagree that the Sigma is too slow to use indoors without a flash. I shoot a 60D/10-22 (wide open is f/3.5-4.5) combination indoors w/o flash at ISO 6400. The results are OK for a hobby shooter like me.

Here is where I have to admit to taking a serious look at the new 16-35 f/4 IS for my 6D. I'll be shooting the same settings, but have access to about 2 stops better ISO performance. Still debating. I can use SOOC jpgs at 6400 with the 6D. No way that is going to happen with the 60D.

f4 is still far too slow for decent results inside a typically (dimly) lit house. Heck, even 2.8 is barely cutting it unless you like grain.

I like Sigma 12-24 but as I said, I have a sneaking suspicion I am not taking full advantage of it's FF capability but am paying a penalty in some added weight, size and slower aperture.

I've been looking at what''s available and there seems to be a bunch of other lenses like Sigma 8-16, 10-20 and this Tokina 11-16 available for crop, and looking at the used prices, it seems I could sell my Sigma (pristine except for a small nick on the hood), get one of these & may be even still have some $ over. Out of these, Tokina seems to have best reviews + at least on paper, have most advantages for trade (faster aperture and slightly smaller and lighter).

But I'd hate to give up a well performing lens without making sure the intended replacement works for me.

I never used UWA until last year when I got this one, and even then only used it sporadically (I mainly shoot portraits). But I started using it for portraits and am really getting hooked.

60D/10-22. f/4.5, 1/100, 6400 SOOC jpgs. I will go down to about 1/50 with this setup, so I have one more stop of useability. Then there is ISO 12800, which requires a bit of work. These come close to working for me, which is why I am considering the 16-35 IS. Two more stops and IS would certainly give me more breathing room. Stuff like this generally works for me, though.