Originally posted by twitch I find that hard to believe to be honest, the DA70 is one of the sharpest pentax lenses available, unfortunately though photozone.de hasn't tested the Sigma to compare directly....
At f/2.4 you are not going to see any difference between the two lenses. Obviously the Sigma is better at f/1.4 - F/2.4 and it has less vignetting and a faster AF. Since there is 20mm difference between the two it is hard to really compare apples to apples. You wont go wrong with either.
If you need wider and faster then the Sigma is the clear winner.
If you need longer and smaller then the DA 70mm is the clear winner.
Nobody is going to tell the difference in IQ between the two. Photozone has tested the Sigma on the Canon 50D, but since that is a slightly smaller sensor with a slightly lower resolution the numbers will be slightly lower.