Why I almost always use a backpack instead of a suitcase

I highly recommend a backpack over a suitcase for all traveling, but especially long term traveling.  

• If you have to run to catch a plane or a train you just do it; you don't have to worry about tipping over your luggage or tripping someone or running over someone's foot.  
• Getting on and off transport is a lot easier as well because you don't have to try and maneuver an oversized suitcase down the aisle and if a bus or taxi or subway is super crowded you can sit with your luggage in your lap instead of having to wait for the next available ride.  
• They're so much easier to store at your hostel, even the high quality ones with rigid backs.  You just squash them flat and shove them in your locker or under-bed storage.  If you're lucky enough to have a large locker, you don't even have to do that. A few times I was able to just chuck the whole thing inside fully packed and lock it away.  Not to mention how much less room they take up in your closet at home.
• Cobblestones.  Dirt paths.  Construction.  Walking a long distance is bad enough in these circumstances, but dragging a suitcase along?  Ugh.  Yes you could always call a taxi, but those charges add up.
• And if you're "backpacking"? Take a backpack!