If you want to compare the devices, you can take a look at my comparison Excel:
https://forum.rme-audio.de/viewtopic.php?id=35156

I would get the UFX II or UFX III, preferably the UFX III.

As nice as the 802 FS is (also from price perspective), tastes are different. I am missing several things, which UFX II and II offer. To mention a few:

• Digital control over Mic Preamps and the headphone output

• The Mic Pres of UFX II and III have a higher gain range up to 75 dB (similar if not same high-quality preamps as in the 12Mic). This gives you more flexibility for "silent recording" when working with dynamic Mics.

• It is also an advantage to be able to store the gain settings of Mic/Instr inputs in TotalMix FX.

• It is beneficial to have AUTOSET as a feature, it makes it much easier to find the proper gain for Mic/Inst inputs.

• DURec is good for performing backup recordings or to use the UFX III as a tape deck for quick recordings without a certain "overhead" of creating a new DAW project.

Newer versions of UFX II have the same analog and digital board of the UFX III, the only difference is now MADI and USB3 due to the higher channel count.

For the UFX III and UFX II, it is also clear that the new Room RQ and Crossfeed are supported. If I recall correctly, then it is not yet confirmed for the 802 FS.

The UFX III is an outstanding versatile unit, the evolution of it I put together in this posting:
https://forum.rme-audio.de/viewtopic.ph … 02#p217002

The UFX III gives you also a certain investment protection because you can easily expand through MADI.

Also consider the amount of work and loss of money if you started with UFX II and then discover later that you need an UFX III because you run out of ports. You can't import the workspace from UFX II to UFX III, and would need to make all your routing and Snapshots again from scratch. If you are using already quite a lot of the ports, it would be better to have enough headroom.

With MADI you have the possibility to expand more easily in case you need more Preamps or AD/DA converter. The AES and the two ADAT ports I would use for connecting other devices like an AXE FX or maybe an ADI-2 Pro reference converter if you like something from its unique feature set.

It is also nice to have a few space MADI channels to be able to create some Submixes for loopback recording.

Normally, no issues are to be expected when using USB3. The RME drivers are rock solid.
But you should take care, as a rule of thumb, 1st of all to use USB3 ports from the chipset.
Because USB from Chipset from Intel and AMD has least problems.

If you have a 3rd party chip on mainboard, then you might get issues. Please check the UFX III manual chapter regarding compatibility. Update on ASMedia: meanwhile, newer ASMedia USB3 chips also seem to work fine.

You can check the reliable USB3 transport of audio data, if you keep the driver settings window open. Then a CRC check is active as long as the settings window stays open, then you can validate, that USB transport is fine, if any of the CRC counter is not increasing.

If you have a spare PCIe slot free, I would recommend that you deploy a dedicated USB3 card only to connect the UFX III.
According to the manual, the FL1100 USB3 chipset is supported and known to work very reliably.
https://www.sonnettech.com/product/alle … 4port.html

I made myself the experience that isolating an UFX+ and now the UFX III from the rest of the USB infrastructure can be very beneficial. Years ago, I had even two UFX+ connected. Over time, I added more and more USB devices and that brought at a certain point instabilities. Since I isolated the recording devices behind such a dedicated Sonnet card with FL1100 chip, there were no such issues anymore.

I am also playing guitar, my setup here.
https://www.tonstudio-forum.de/blog/ent … iii-en-de/

An UFX II would have given me already limitations as I am using plenty of ports for my stereo setup with two amps and two Lexicon FX (PCM 81 and 91). The nice thing here is, that simply by TotalMix FX routing I can use the Lexicons as I want
- one or two for Guitar or for Cubase or
- PCM81 for guitar (because it has modulation effects) and PCM91 as a reverb unit for the DAW (which is my default setting)

I am plugging my guitar to the UFX III to be able to use VSTi and to re-amp.
I am also using the UFX III as a parallel effect loop.
From the Marshall's preamp, I go back to the UFX III and distribute the signal
- directly to the power amp section of the two amps to keep the "punch" / the dynamic and
- then to the Lexicon FX and add FX 100% wet to the power amp section of both amps.

And from the Instr input I am sending the signal additionally to a rack tuner, a Korg Pitchblack X Pro.
Nice additional use case: when adjusting fret purity to have an additional control in addition to the ear.

If you are interested in MADI or want to take a brief look at the implementation, it's easy, you only need to know a few things. I put together something last recently in this posting:
https://forum.rme-audio.de/viewtopic.ph … 32#p217332

That's a good decision, you will like it and enjoy it for a long time.