I have a few good reasons for that:
-I wanted to be sure that the "SR-Lambda" I had, with the mineral wool removed, the rebuilt drivers, and a 5-pin Pro bias cable for whatever reason, was indicative of a real SR-Lambda in stock condition. It turned out not to be, not by a long shot. These last two years left me kinda deceived, actually.
-Word is that the original SR-Lambda has the best midrange reproduction of the entire Lambda line. I don't want anything getting in the way of my vocals.
-I didn't like the Nova/numerical arc due to significantly higher clamping force, but it actually turns out that a vintage arc in good condition clamps almost as much, and my first set is just unusually loose in that regard. For this reason, I may start looking into the Lambda Nova Signature once more, provided that I can find a set for sale.
I'm no expert, but if your other "Lambda" was driven on Pro bias there's a possibility the drivers may have deteriorated.