These are my favourite marking tools. I recon I have used every tool invented, and come back to these two. The white Clover Pen comes out in the wash or it irons out. The first time you use this pen you will probably think there is something wrong with it. It draws on clear, but as you wait a minute or two, the white line appears. I love it for all kinds of marking on darker fabrics. The blue wash out pen never lets me down. We have all heard the horror stories about the lines coming back etc, but that has never happened to me, and I have been using it for over 15 years - or a variation of the pen. The newer ones have a fine tip which I love.
I have used chalk pencils, that did not come out, and ceramic pencils that also left marks in my fabric, so I stick with what I know works for me. When marking, I have them both in my hand, and flip from one to the other as I move along the fabrics.