I am only 153 cm tall, I use MM size, I think PM is too small, it cannot hold the A4 fle. I think MM is quite useful. Of course, I can't put very heavy things inside. But as usual, I put my wallet, card holder, key holder, coins bag, cosmetics bag, hand cream, mobile, it;s quite OK for me as it is not too heavy, and the shape doesn't change.
I think GM is much suitable for the one who is taller than 160cm. It is TOO BIG for me.