I think you'll find it's all personal preference, like shoes. I happen to like the suitcase because pulling it seems a lot easier to me, in most cases. There are some instances where I can't (gravel parking lot, through snow, etc.), but it doesn't happen too often. Others prefer the over-the-shoulder bag for those reasons. I try to get the smallest rolling suitcase available, so that my things tend to fill it up, and they don't shift around while moving it from place to place. Maybe you just need a smaller case?
Then there are some forum members that use those PODS portable units since mere suitcases would never hold all of their gear, right Tanner?
