I have a few of the McFeely screw assortments in both the Box Systainers and the 12-Drawer Sortainers. Each type storage unit has its own advantages and disadvantages.
The 12-Drawer Sortainers provide access to their contents without having to remove units that may be stacked above. Each drawer can have its own label so you can readily identify what is inside and have instant access. And, Sortainers come with drawer dividers, so you can separate items within a drawer. I've only had an occasion or two where the drawer became stuck due to something shifting within the closed drawer, and didn't find it too difficult to a time getting that resolved -- but, I don't transport these very much at all, as they mainly stay in my shop.
The Box Systainers come equipped with a hard-foam lid insert that covers the boxes when the lid is closed. This prevents any of the contents from getting mixed up and there are no drawers to get stuck. I have the original 'Classic' Systainer 1 Box units which don't allow access to their contents within a stack. The newer T-Loc Systainers might allow you to gain access where the Classics do not -- but how well that works may be dependent on what all is stacked above...
Either type will allow you to take an individual box or drawer out from the Systainer/Sortainer and take it to where you are working, which is handy. My preference has been to keep screws in the Box Systainers and nuts, bolts and washers (or other hardware) in Sortainers. Both type storage units are nice to own, and you will likely find a use for either type. So, why not order at least one of each? You can always order another and swap the contents as desired.
