I think that it would depend on the amount of machine embroidery that you want to do, and the actual garment that you are making.
If it is a large amount of embroidery you may find it wasier to work on a more stable fabric such as cotton, although you need to remember that when the fabric is being embroidered it is placed in a hoop and pulled taught so you may be able to complete all of the embroidery fairly easily without too much fraying of the fabric.
I think also that it is dependant upon how you feel about working with different types of fabrics, you need to be confident with the fabric that you are working with for it to be successful.