Hi rmesp and welcome to the RME user forum.
You can get the differences between different RME recording interfaces from my Excel file, see here:
https://forum.rme-audio.de/viewtopic.ph … 26#p186126
These differences include very fast converters (same low converter latency like in the ADI-2 Pro FS R BE). Also, improvements in the analog section, DC coupled outputs, USB3 CC mode for all I/O ports, FS clock, track names for DURec, remappable (33 functions) and lockable keys. The latter two features were first introduced for the Fireface series by UCX II. Additionally, both ADAT ports on the UFX III are switchable to optical S/PDIF.
If I were you, I would invest in an UFX III to have MADI which means more options for the future.
These threads also contain some information of interest:
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13