Mostly I travel with a soft leather bag. It fits everything I usually need and it works as a carry on.  If I'm traveling overseas, then I use hard luggage. 

I do the same as Mary does. For short distance travel, I use soft bags or sometimes back packs. When I travel abroad, its a combination of both the back pack (for hand carry) and the heavy and hard luggage.

I generally use a soft-side suitcase but I do own both types. Whatever I use on any specific trip now always has to have wheels. I've learned the hard way that wheels are a necessity if I want to have any measure of comfort on a long journey through an airport.

Soft is easier for me since right now I still have some damage to my right shoulder (its here for the long haul). If I can avoid having to lug heavier stuff, I will, its just easier that way for me.