For most of my trips to Asia I have taken backpacks rather than cases as they are more practical. This is mainly for beach and island trips because many areas don't have pavements, so trying to wheel a case isn't practical. Also on one trip it was by boat, and a suitcase was not a good idea, and even with my backpack, I learned to put everything in waterproof bags too.
Why, if you get a bus, they put the luggage on the rack ontop, and that means if it rains, things will be very wet.
Do you consider this on a trip? If not, it's worth thinking about, or taking a soft sided holdall that is easier to carry.
I always prefer a suitcase, but I have found it impractical at times. I was in Italy and trying to roll a case down a cobbled street was hard work as it kept falling over, and in rural places there is no smooth surface. Also places with lots of steps make it much harder, and so a backpack makes it easier.
I remember one hostel I was staying at was up a hill, and so I had to try and carry the case up. Fortunately some other tourists saw me and helped me. At that point I wished I had a backpack instead.
We travel often but we don't have a suitcase. Our things are kept in a bag. A suitcase is bulky and heavy to carry while the bag is more convenient and can easily fit in the overhead compartment of the plane. Besideswe are llight travelers and we don't bring much baggage so we don't need a suitcase.
I think it depends on where you're going and how long you're staying. If I know that I'm going to spend the majority of my time on a business trip and in a hotel, a suitcase is a must for all the extra things. But if I know I'm going to take a lot of buses or trains as I bounce between towns and cities, I prefer a backpack or at least a small suitcase with wheels. I usually do both. The suitcase stays at the hotel or hostel and the suitcase stay there while I travel with a backpack. I tend to replace my purse with a backpack because it carries more.