14.2L, Mini-ITX
CS01
CS01-HS
Same chassis, different configurations. The CS01 is meant for internal storage whereas the CS01-HS stands for "Hot Swap" and as you can guess, has hotswap 6x 2.5" bays that are accessible from the top of the case, with an additional 2x 2.5" internal mounts.
Personally, I could see myself using the CS01-HS, especially as I'd like to transition away from mechanical drives even for storage purposes. Not too interested in the CS01 - I think the M1 actually makes a better, smaller, albeit more expensive fileserver than it, to say nothing of other options.