I went through my comparison Excel to find out the differences, to make it perhaps a little bit easier for you, to take the flagship models UFX II or even UFX+ into consideration.
Some might argue, that an UFX+ might be overkill, but keep in mind two important things:
1. when using higher sample rates the loss of channels in double speed is with ADAT only quite severe. So it might be a good thing to have also MADI for any future demand in the future without having to get a new recording interface. Those free MADI ports can also be used very nicely for loopback recording. You do not have to waste analog or ADAT channels, if you need them for other purposes
2. Its always a big advantage if you have different possibilities to connect to the PC. I remember myself that in some cases USB worked better for me compared to Firewire with a certain Mainboard. With USB2, USB3 and Thunderbolt (external PCIe) you have a wide range of options to use the best / most stable connection towards the computer.
Here a comparison between 802 and UFX II / UFX+ over the 802:
higher quality analog section
higher mic gain (75dB vs 60db gain), higher input level of +18dBu (vs +10), little higher SNR (118 vs 116dBA)
digital gain control, Gain can be saved/restored in TotalMix FX
better / stronger phones outputs with lower output impedance
Hi-Z instrument inputs (1 MOhm vs 800kOhm)
Autoset (automatic overload protection that also can be used to quickly/only find the proper gain for recordings)
DURec, direct USB recording on USB sticks, etc. for backup or stand-alone recordings, also in CC mode for iPAD
Internal real-time clock to get timestamps for files on DURec recordings, easier to identify recordings by this
uses the newer MADIface USB driver that allows sample rates down to 32 (vs 48) samples if needed
New ARC USB can be connected to a special USB port on the back for this purpose, also nice for stand-alone operation
100% fully standalone operation through the Display
UFX+ can be connected to PC in three ways: via USB2 (without MADI), USB3, Thunderbolt
UFX+ can be expanded through MADI (more channels available at higher sample rates compared to ADAT only solution)
UFX+ "MIDI over MADI" to control Mic Preamps (Octamic XTC, soon also 12Mic) without the need for separate MIDI cabling
802: "old" ARC for remote control also in stand-alone mode is not available/purchaseable anymore
Differences between 802, UFX II / UFX+ in terms of loopback operation:
802: pre-fader, UFX II / UFX+: post-fader
The loopback function in TotalMix FX is implemented either "pre-fader" or "post-fader", depending on driver and hardware support. The "pre-fader" implementation allows to mute the HW output without affecting the loopback operation.
This is useful, for example, to mute connected active monitors without disconnecting the cables.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14