What's the difference between Knit 1 Below (brioche stitch) and knit one color A, knit one color B?
Oh. Hmmm. With every row of two color brioche, you are effectively undoing one of the previous rows...in other words, you have to work 4 rows to get two physical rows. See?
Well, no of course you don't see, because the big difference between the two methods (aside from the time it takes) is the interlinking on the back. The brioche has a nice, clean finish; two-handed fair isle is neat, but I would never use it if I thought people would see the other side. You can see the difference pretty plainly right here:
Now we all know the answer to this question!