1) In crowded areas, either in the airport, on public transportation, or when arriving in big cities, the wheeled luggage can easily be rolled alongside you (when pulling the bag behind you is not possible or difficult). Just rest your hand on the handle and walk; the bag moves easily besides you!
2) Same concept as above when making your way to your seat through the narrow aisle of the airplane, the spinner can be rolled in the upright position, easily gliding through the plane without hitting protruding armrests or elbows.
3) The weight of the bag is self supporting, spinner luggage does not tip as easily
4) Easier to maneuver on escalators and other awkward spaces
5) Less strain on your back and arms
1) If a spinner is not secured on a slopped surface, it can roll away
2) The wheels protrude out slightly thus there is a greater chance of a wheel breaking or snapping off. If you use carry-on spinners, not succumbing your bags to the baggage handlers, there is a smaller chance of this occurring.
3) Slightly higher priced