Unless something has recently changed, the SFF Precisions and Optiplexes used weird smaller PSUs and generally have really poor airflow. Generally the lower end precision mid-tower also flow air terribly and get hot and whiny. There's no way I would recommend an SFF system if you can get the MT variant, as your options for fixing the MT systems when the Dell PSU inevitably fails are much better than getting a regular ATX PSU, cutting a hole to feed the cords in, and bolting it to the side of the case, which I've done repeatedly for SFF Dell systems with blown PSUs.

Additionally, one challenge I have with all of these is that none of them have anything like a BMC. If you have more than one system, moving peripherals around sucks, and KVM technology is kind of iffy these days. It seemed easier to just jam an old Supermicro motherboard that had IPMI enabled in a reasonable ATX case with a lower power Xeon variant, and call it a day.