Originally Posted by Macybaby

A lot has to do with the orientation of the bobbin and if it's full rotary or oscillating. Many quilters prefer the Singer 15 to the 201 as the 201 is full rotary and because of that puts an additional twist to the thread, which can result in a more pronounced slant. For seaming it's not a big deal, but one likes nice straight stitches for Quilting as they are visible.

it would be interesting to compare this to a VS machine, as I don't think the thread is twisted at all with that motion.