I have had a royal ball winder for several years. It winds well and generally makes me happy. However, I like to hold it in my hands instead of clamping it to a table, which will give me hand cramps after a skein or two.
I was very excited to see that the knitpicks winder comes with a handle attachment. I ordered one (and my husband didn't know that and ordered another one for my birthday). Sadly, I am disappointed. It is more ergonomic, but the yarn tends to find its way under the cake that is being wound VERY often, causing a tight bit of a mess, and interrupting the winding process. Also, the ergonomic handle doesn't lock in that well.
I am usually quite happy knitpicks products, and still love their metal options set, and their harmony dpns.
Hope this helps some of you who are shopping around for a winder.
Royal trumps knitpicks like rock crushes scissors.