I started my career with an old school Craftsman top and bottom chest. While it worked great for working on the farm and doing side work through high school, it didn't handle the hard life of day to day wrenching and I quickly realized it didn't like being loaded as heavily as I was needing to load it at work. I bought an older used Snap-on from a co-worker that seemed to handle the weight a bit better without flexing or drooping but with it having friction slides it was not the easiest to open and close the heavier drawers.
After several years I traded that in on a used Matco with roller slides and it was much better. Used that box for several years without issue. From there I upgraded to a dent and blemished MAC Macsimizer with two side lockers and all roller slides for my home shop and bought another slightly used Snap-on top, bottom and short side box for work as my home tool collection was outpacing my work tools.
Used the MAC Macsimizer box at my home speed shop until early 2007 when a friend of mine from high school became my local Snap-on dealer and he made me a great deal on my current Snap-on KRL bottom, top and side locker which I still currently use daily. This box is hands down the best tool box I have ever owned and probably will have it until the day I die. The drawers are loaded extremely heavy and the box doesn't even moan about it.
My KRL1023 bottom, KRL1203 top box and KRL1012 side locker. This box still looks and feels like new, other than a few minor scratches, despite being used daily for the past nearly 15 years now.
My top full width top drawer is probably the heaviest one in my entire box being loaded with sockets.
Next heaviest is another full-width drawer being loaded with wrenches.
The heaviest single width drawer has to be my impact tool drawer and none of these have any issues opening or closing when loaded with all this weight.
Seems like toolbox's hadn't changed much for the first 25+ years of my career with the quality ones still being found mainly on tool trucks with the small exception of maybe Lista modular style but still high dollar amount needed to be shelled out to get a quality box. However it seems as though they have come a bit further over the past decade or so though. A couple of our newer mechanics at work have either Husky, U.S. General and now an ICON and I have been somewhat impressed with the bang for the buck of these toolboxes.
Nearly five years ago now when I built my new shop I sourced five (5) of the U.S. General boxes from Harbor Freight to incorporate into my workbench design and I have been pleased with their performance thus far. I don't have them loaded anywhere near as heavy as the drawers in my Snap-on box but they have seemed to hold up well for their intended purpose.
I have been quite impressed with the build quality of the Husky a co-worker has although I personally don't care for the looks of it. I am really quite impressed with the new ICON that the guy just rolled in a couple of weeks ago so we'll see how it holds up long term to the day to day use but I really don't see that being an issue as an initial gut feeling based on what I've seen so far.