I read that felting shrinks your pieces more lengthwise than it does widthwise, so I decided to do some experiment as soon as my new felting wool arrived. All yarn shown here are 100% wool. This was done by hand felting.
I also did both knitted and crochet swatches as there is not a lot of literature on Crochet Felting and I wanted to see for myself what the difference was and why it seems less popular than felt knitting.
I am sorry I forgot to take photos of the pre-felted pieces. (It was late in the night and I was too eager to knit and felt for the first time!) So all I can do now is draw outlines that, though not the real size, are to comparative scale so you can visually see the shrinkage from felting.
As you can see, my crochet swatch sample has shrunk more width-wise than it has length wise. I cannot guarantee that this will always be the case as this is only one sampling. But does at least say that the shrinkage you will face when you are knitting vs. crocheting with an aim to felting them, can be very different.