I have a couple with the stretchy things, a couple with the slidey-things, and a couple of Sys3 versions with the latch (y thing?).
The stretchy thing models have the smallest overall footprint. They also have smaller casters than the slidey version and the latchy version.
The latchy version is ever-so-slightly narrower in overall width compared to the slidey version, but deeper front-to-back. At a glance, they look larger in both dimensions, but the specs and my tape both say different.
I think I have a stack of tires on one of my stretchy models. I got it used, but it's still quite a bit more expensive than a wooden trolley cart from Harbor Freight.
All of the Festool models roll much smoother and nicer than the HF or Menards models, though.