Regular Lambda is different and it's quite nice in its own ways, even though the Pro, in my mind, is the clearly superior headphone. But it's still a Lambda, you know? (i.e., different, but not worlds different.)
I say get a SR-X mk 3. I swap between my Lambdas and the SR-X and I like having both. Overall if I had to give one up, I'd keep the SR-X, as it's a fairly unique presentation.
Best,
-Jason