You can use my comparison sheet to compare the two to each other.
https://www.tonstudio-forum.de/index.ph … 18-08-pdf/

I would take the UCX if you can afford it for the following reasons:
- newer converter
- preamp technology from Micstasy
- Autoset
- six at the device recallable standalone setups
- FX chip on board
- Class Compliant
- USB and Firewire (if i.e. Apple Mojave has USB issues, then you could use Firewire or a TB to FW adapter shall your Apple support TB)

Regarding FX section:
TotalMix FX is the new product name after a major overhaul of the software. So you need to look closer at the product description (Web, manual) whether a recording device has a FX chip or not. UC has no FX chip.
Most people use FX in the DAW because there you have more CPU power, can run more complex and a variety of delay, reverb and other effects.
On the other hand I have to say that I personally regard the FX section as very useful.
You do not have to take care by DAW routing, how a vocalist gets a little reverb to feel more comfortably when recording
and I use it very often for my HiFi to give a little Bass Boost when I listen at lower levels and other things.

Autoset I regard as extremely useful, by using it it's very easy to find the proper gain level of each channel.
Then I can simply raise the gain a little lower, then strum the guitar or raise the volume of the amp
and then I have a perfect level for recording. It's simply more comfortably.
And there are situations where you want eventually to use it permanently for a recording to ensure, that no clipping happens. But then you need to take care that nobody bumps on the mic, because this would lower the gain permanently.
Autoset only reduces the signal to prevent clipping.

Class compliant mode can become very useful if you intend to connect the unit to Linux, this is one of the prerequisites that Linux / ALSA can do something with the device AFAIR. Also required if you want to record with an Apple iPAD. This gives you a broad field how your recording interface can be additionally useful.

The 6 stand-alone profiles I also regard as extremely useful. You can use TotalMix FX on your PC to prepare for a certain routing and settings that you need very often, then digitally store it on PC and finally transfer the settings to one of the 6 "slots" on the device. When the UCX is not connected to the PC you can recall these prepared settings at any time.

If you need things like this more often then I even would recommend to look at the UFX II.
There you have a bigger display which enables to you operate the device even without PC in standalone mode
and other cool features like Durec, to be able to record directly to USB stick / disk / ssd.
I use my UFX* very often as tape deck. Not having to fire up DAW for recordings, which is for overdubbing sessions
more comfortably.