My take on two or four wheels: it depends where you're going to use it. Four wheels work well indoors, such as along the concourse in an airport, but are hard to get over curbs and broken pavement outdoors, which two-wheeled bags navigate easily. The wheeled bags that I use are bags that I check; the bag that I take to the gate isn't a rolling one. Since I often go from airport to hotel and back on public transit, I use a two-wheeled bag.