Connecting Kemper to audio interface (in my case an RME UFX) - Main Out specs

Hello, I just bought a Kemper Power Rack. I use it in my home studio and I connect it to my RME Fireface UFX using Win 10.

I tried two ways of connecting it to the audio interface:
- the XLR Main Out to a couple of the four XLR mic preamps of my UFX
- the Jack Main Out to a couple of the Line In inputs in the back of my UFX
I set the Line Ins of my UFX to -10dbV since the Kemper signal through the unbalanced outs was quite weak.
I then tried to record a guitar part to two tracks at once using the mentioned connections.

By listening to the two recording, the result is not the same. I feel transients are better and the signal is generally better through the XLR connection, even after normalizing both the tracks in the DAW
Shouldn't the two signal be the same? Is the Jack Main Out from the Kemper actually conceived to be sent to an HI-Z instrument input on the audio interface?

I didn't try the SPDIF connection since I would need a coaxial-to-optical converter and I use already my UFX SPDIF input for basic Windows system audio

Regards,

Andrea

Well thank you for your hints, they were helpful, but unfortunately the UFX only accepts one SPDIF signal at a time, either from the optical or the AES connectors. Since I already use an optical SPDIF from my ASUS motherboard I would then need a multiple AES to single ADAT converter and I should also get a coax spdif signal from my PC motherboard (I know there's some SPDIF jumper on my ASUS Z-97 AR) or an optical-to-coaxial..
Actually I got no hints about analog signal routing from the Kemper to audio interfaces, the manual doesn't say much about it, it only tells about mixer routing but no mention about other applications of the Kemper other than mixing desk or live mixer connections.