Originally Posted by
Prism99
Topstitch needles have a larger eye, which makes them easier to thread.
They also have a long scarf, which is a groove that runs the length of the needle. This gives the thread a place to rest as the needle moves in and out of the fabric, thereby reducing friction on the thread. I personally don't think this matters much when piecing, but is invaluable when quilting.
I don't have much of a problem with large holes being left behind by quilting with a larger needle, because 95% of my quilts are washed after completion, and the holes close right up. I use a size 12 or 14 for piecing, and a 16 or 18 for quilting.