There are plenty of differences between UFX and UFX III and the later versions of UFX II.

Let me give you a brief overview about the flagship devices, you can also gather information from my comparison Excel:
https://forum.rme-audio.de/viewtopic.php?id=35156

To give you a brief history, in what order / when the different models have been introduced:
- UFX 2010
- UFX+ 2016
- UFX II 2017 (same as UFX+ but without MADI/USB3; later versions got ESS converter due to chip crisis)
- UFX III 2023 (with AKM converter from ADI-2 Pro FS)
- UFX II ~2024 (with same analog/digital board of UFX III, the only difference: no MADI/USB3)

There were already plenty of differences between UFX and UFX+/UFX II:

As you can read here in my blog: https://www.tonstudio-forum.de/blog/Entry/68-RME-UFX/
Here are the differences from that article in compact format:

• Revised version of analog circuits and DSP

• improved SNR and THD values

• DURec: up to 76 channels can be recorded simultaneously — optionally with 12 analog and 64 MADI inputs

• DURec: internal RTC (Real-Time Clock), allows timestamps in DURec recordings

• DURec: increased reliability when using slower or multi-partitioned USB thumb devices

• DURec: support of multiple FAT32 partitions, the last active partition is automatically reactivated after a power-cycle

• Microphone inputs with + 18dBU max, no PAD

• Microphone inputs with 75 dB Gain Range

• Headphone outputs with only 2 ohm impedance, with +19 dBu max output level

• ARC USB pluggable also directly pluggable to the UFX+/UFX II, useful for stand-alone operation

• The two rotary encoders on the right of the display now individually adjust the volume of Phones 9/10 and 11/12.

• Fully operable stand-alone, there are additional settings compared to the UFX.

• New MADIface driver supports smaller ASIO buffer sizes down to 32 samples (UFX 48 samples)

• MADIface driver supports many new devices and thus allows the application/DAW direct access to various RME devices in "multi device operation": UFX+/UFX II, MADIface XT/Pro/USB, OctaMic XTC, ADI-2 Pro/AE/FS/DAC, Digiface USB/Dante. You only need to take care to clock sync and to use the same ASIO buffer size.

MADI related feature only for completeness:

• USB3 / USB2, Thunderbolt connection to Windows / Mac, supports "hot-plugging" under Windows

• Additional 64 channels by MADI with the options auto, optical, coaxial and split

• total channel count 188 channels (94 IN, 94 OUT): 24 analog, 32 ADAT, 4 AES, 128 MADI

• Word clock BNC switchable to MADI coaxial

• MADI split mode allows 32 channels each via MADI optical / coaxial

• MADI I/O via TotalMix is still available on USB2, despite the limitation to 30 I / O inputs (12 analog plus 16 ADAT plus AES)

Followed by new features introduced by UFX III and also an overhaul of later UFX II models

The differences, you can read in my blog: https://www.tonstudio-forum.de/blog/ent … iii-en-de/
Here are the differences from that article in compact format:

• A new analog section with improved SNR values and 6 dB better THD+N.

• The digital section has also been revised, and the UFX III now features 3 separate AES/SPDIF receivers and transmitters, enabling both ADAT ports to be switched to optical SPDIF.

• Room EQ and Crossfeed (by firmware upgrade), see also info below

• FS (femto second) clock.

• High-quality converters from AKM (AK5574 as AD converter and AK4490 as DA converter), which are already familiar from the ADI-2 Pro FS.

• Fast converters with only 5 samples of AD latency and 6 samples of DA converter latency.

• All analog outputs are now "DC coupled" and suitable for controlling synthesizers.

• Track names for DURec, where the user-defined channel names in TotalMix are adopted as track names in DURec recordings. During the subsequent conversion of the DURec multichannel files (using RME's WAV-File-Batch-Processor 1.31), individual channel files receive the track name as the file name.

• Remap Keys enable the assignment of 33 different functions to the four direct selection buttons on the display.

• Lock Keys allow deactivating only the four front buttons or even the three encoders (first introduced with the UCX II).

• Only for UFX III: USB3 CC mode allows the utilization of all 94 I/O ports, regardless of whether for Linux, Mac, or iPadOS.

Information about Room EQ

https://forum.rme-audio.de/viewtopic.php?id=38691
https://forum.rme-audio.de/viewtopic.ph … 43#p210543

See also this useful YouTube video about "Using RME ROOM EQ and Sonarworks to calibrate your Home Studio"
https://www.youtube.com/watch?v=ThnD4__RMB0

To sum up

UFX III and the later versions of UFX II offer you a lot of very useful features, and also the new Room EQ and Crossfeed.

If you are not limited by budget, the UFX III and UFX II are out of question the products to go for. By more features and better upgrade possibilities (due to more powerful FPGA, example Room EQ) it also gives you more value for the money and a longer investment protection.

If you think you do not require those new features, then it is your decision / choice.