Here is how Cavalli Audio explained the changes in Gen 2 vs Gen 1:
"This final run of Carbons will feature a 2nd generation power supply, which has been designed specifically to reduce noise from the single-ended output. Of course, we highly suggest that you run your Liquid Carbons with balanced output to get the most out of it, but we’re doing what we can to improve the SE output anyway… for those times when you just don’t have the appropriate balanced cable on-hand. See, that’s a good surprise right?
Oh BTW, we’re also including rubber feet this time around! I know, it’s only rubber feet… not exactly a big deal… but since you guys asked for them, we’re including them."
Comments in this thread imply some users had channel imbalance issues w/Gen 1, possibly related to the phase splitter: this issue was corrected & the power supply improved, in Gen 2.
I have used my Gen 3 (purchased in the 3rd and apparently final production run, ~5 months ago, for both SE & balanced, but mostly balanced. The sound is amazingly good both ways, but subtly better via balanced, in the ways one would expect (slightly more spacious soundstaging; occasionally a slight benefit in bass, very headphone-dependent).