The new hEX (RB750r3) runs RouterOS 6.x which is the latest major RouterOS release. Some known limitations..the new hEX/RouterOS v6.x doesn't support:
Btw, EdgeRouter X supports all above features (but as I mentioned before and elsewhere, UBNT cripples ER-X in a different way).
- automatic QoS such as fq_codel
- IKEv2 IPsec VPN; IKEv2 is more efficient than L2TP
- per-port VLAN configuration; HW is capable but currently not implemented in FW
- VTI for IPsec tunnels
Btw, EdgeRouter X supports all above features (but as I mentioned before and elsewhere, UBNT cripples ER-X in a different way).