One way of categorizing Hyperconverged filesystems (or any filesystem really) is by how data is distributed across the nodes, and the method used to track/retrieve that data. The following is based on knowledge of the internals of Nutanix and publicly available information for the other systems.
||Distributed data & metadata
||Random data distribution, hash-lookup (object store)
||Data stored in HA-Pairs, Lookup by fingerprint
||Random data distribution, Lookup by fingerprint
||Data stored in HA pairs, Unified namespace via redirection
Nutanix uses a fully distributed metadata layer that allows the cluster to decide where to place data depending on the location of the VM accessing it. The data can move around to follow the VM. The Nutanix FS uses a lot of ideas from distributed systems research and implementation, rather than taking a classic filesystems approach and applying it to HCI.