I couldn't find much information on the Dewalt Tstak and Craftsman Versastack systems so I thought I'd share my experiences. Verstack was from Lowes and Tstack was ordered from Amazon.
First of all, these two systems are completely compatible. You can see in the first photo how the two systems nest together.
The clips, while difference in design, function similarly and lock into the upper box perfectly. You can see in second and third images how the clips are different in shape and construction. The Versastack (black) has metal rods attaching the clip to the box while the Tstak (yellow) is completely plastic. I'm concerned about the longevity of the Tstak plastic clips as I've seen them break in other reviews. When I need to move multiple boxes, I will do so separately and only keep boxes clipped together while standing on the Tstak cart (DWST17889).
I've combined the Tstak deep long handle tool box (DWST17814), Versastack 2-Drawer (CMST17804), Tstak Single deep drawer (DWST17803), Versastack bin (CMST17809), and Tstak cart (DWST17889). The stack in picture 4 is about 4 1/2 feet tall. I keep larger power tools in the bins (grinder, jig saw, recip, circular saw, kreg jig).
The last photo with the open drawer demonstrates the depth of the Versastack 2-drawer box drawers. Keep in mind these drawers are very shallow. Almost too shallow for what I wanted to use it for. The 3/8in sockets on the organizer is just short enough to get the drawer to close. All the photos I've seen Versastack 2-drawer box show it as just a small parts organizer. With a little bit of customization and organization, these drawers can fit a good amount of tools rather than parts. The milwaukee M12 ratchet barely fits- the rubber overmolding rubs on the upper drawer but the drawer does close.
I'm coming from the Husky 22 in Connect Rolling System. Comparing the construction of the Husky and Versastack/Tstak systems, the Husky wins hands down. Versastack/Tstak is much thinner in construction all around. However, this is acceptable for my needs. As a DIY'er, organization and ease of access is more important than tool box strength. I often think of Adam Savage's first order of retrieval methodology (watch Tested on Youtube) and drawers for me are just that.
We don't have many big box tool stores aside from Home Depot and Lowes here in Hawaii. Amazon ships tstak boxes for free with prime. I bet they're going to change that soon. Does anyone know if the Versastack system is going to be discontinued? The Lowe's here have them all on clearance.