Hi,
I also vote for the leather ones. I have more than a dozen of them scattered through out my house. Since I am a hand quilter for hire I usually go through one everytime a do a full size or larger quilt. I also quilt with both hands so I use a shorter black leather one on my left thumb. When I quilt left handed I push with my thumb. The leather ones I like best are made of deerskin, have a plastic round disk in them and elastic that helps them stay on. I get them at quilt shops and have gotten some of them through catalogues etc. I prefer the ones that are light brown. I even have a pattern for making my own but haven't used it yet. I have never learned to use a metal one.