First off, welcome to the birdforum. The low light differences between any of alpha 42's is going to be very slight. Having said that, low light comparison is something I've spent many hours doing.
In 42mm I previously owned the Victory SF, and Leica Ultravid HD+ 7x42. At present I have the Victory HT, Victory FL 7x42, SLC-HD, and recently discontinued SLC WB. To my eye the absolute best is low light is 8x42 SLC WB. In fact, the two Swaro SLC's are the best I've ever looked through period, and that includes the NL Pure (which I've checked four different times at length in outdoor conditions).
It's personal preference, and many will prefer something else, but I can say without reservation that the SLC's are the only bin I've ever used where I did not ask myself if I would be able to see the subject better through something else.