I use lots of polycottons and they are great for applique as the cotton fabrics are so thick. Also there is the question about if it will last well it seems that my polycottons last longer than the cottons. cottons fade much quicker than polycottons. Another thing to consider is the cost of the cottons. So I just buy what I like and what is available and make do.
You must decide for yourself. here we do not have as many choices locally and sometimes use blankets for inners. take care and enjoy your quilting