I doubt anyone has a single brand throughout their box. Each company makes a tool that is needed for certain jobs. Snap-On is nice, but sometimes their tools won't work in some spots (7/16 sockets on generator terminals, for example), which is why you have to have a selection from different manufacturers. Most of us figure if we borrow a tool twice, we need to buy it for own box. I keep a drawer full of Craftsman wrenches and sockets (Metric and Standard) in my roll-around in case I need to make a custom tool for a specific job.
A lot of mechanics will build custom boxes by combining Craftsman boxes and welding up a support frame with heavy duty casters. If you can afford it, try to buy a box with good sliders and look to see if the base is reinforced. For a long time Craftsman boxes had construction problems. The drawers were flimsy and would sag, and the bases would get beat up and the casters would pull out if moved around too much. Now Craftsman is offering much better products in the middle of their line, but I still suggest looking for a used box from a tool truck.