There are a few factors to consider when purchasing a tool bag on wheels. The size and weight of the bag are important, as you don't want something too large or bulky that will be difficult to maneuver. The number of pockets and compartments is also key, as you'll want to be able to organize your tools in a way that makes sense for you. And finally, the durability of the bag is important - you don't want something that will fall apart after just a few uses.
With all of that in mind, we think the best tool bag on wheels is the Milwaukee Jobsite Work Box (model number 48-22-8400). It's made from durable polycarbonate material, so it can take a beating, and it has plenty of room inside for all your tools. Plus, it has compartments on both sides for easy access to whatever you need.