Alright being that noone seems to be chiming in with the right info i'll give you the basics.
The quiafe and the torsen are relatively similar and they are both LSDs. the torsen is not a locking diff. the difference between the two is the amount of split between the wheels. I believe the quiafe is a 60-40 and the the torsen is a 65-35(might be a 70-30) i'm not positive on the numbers but i do know that the quiafe has a more even split than the torsen. They are both very good pieces and fuction extremely well when it comes to autocross. The difference between the two is very minimal between performance but the fact that the quiafe is rumered to have a waranty is worth looking into. As for the price i believe the difference in performance is not worth spending the extra couple hundred but if the quiafe has a warranty and thats something that you feel is nessary then you might not feel bad about spending that extra cash.
I myself went with the torsen t-2 diff for the focus. You can notice right from the start that it is a very well put together part. When you accelerate hard from the apex of a corner you can feel the torsen working as it jurks you around the rest of the corner. Also when you go to warm up your tires for the strip you notice that both tires are now spining the way they should be and you don't have the one wheel wonder that the factory part gave you. I have been extremely pleased with my t-2 diff and would not hesitate to buy another one. But after the abuse i've put mine through and the fact that it's holding up just fine i'm sure i won't have to.
358whp and 335tq on 93oct.