Modern technology and innovative design have made the hard sided luggage easier and cheaper to make. Meaning the difference between soft and hard material has become less apparent. Both soft sided luggage and hard sided luggage has their advantages and disadvantages.
Nowadays you can get similarly durable, lightweight, and priced, soft and hard-sided luggage. It can therefore be only a matter of preference, which type of material to go for. Besides, if you buy a good quality one, both soft sided and hard sided luggage is durable.
Hard-sided luggage though still offers the best protection while soft-sided luggage offers more flexibility (can be expandable with an expandable layer and with external pockets, etc).