It’s a matter of weight, price, security, amount of use. Each person has different needs
I have had hard luggage and found I need it once or twice a year, 10 day Europe trip and possibly another. Decided hard luggage whilst convenient was heavy and too wide for filtering and big outlay for minimal use and pain to store safely. Went away this year with 52L trekker top box and Givi 40L roll bag strapped to my seat. Still came back with unworn items after 9 days.
Looking at the Lomo bags for £70 but will wait til they are back in stock. Think they do what I need for panniers and very good value.but will need to make adaptions. Need heat shield (thin alu checker plate) to stop them touching exhaust and melting, and some light inner bags so can leave pannier bags fastened to the bike. I will make sure they are securely fastened for whole trip by the straps and some zip ties
The other benefit of soft luggage is if you drop the bike they act as big pillows and you don’t damage your bike
Lots of choice and prices......horses for courses depending on your needs and cost