I too have heard from a LQS that you should always use the same brand of rulers, what made me skeptical was that statement was followed by a sales pitch for these new wonderful rulers. I do have my favorite rulers but I use what I have on hand just as I would use whichever tape measure's in the tool box when cutting wood. Seems to me that the variables would come more from having human eyes, thread thickness and general sewing, as in all quarter inch feet are not created equally. We all find out what works best for us, as long as we're learning and enjoying the process, right.