I have both the LDRxB-V2 and the LDR1B-V2. The LDRxB-V2 is the main preamp/controller for the system to switch inputs and polarity.
I've found that the LDR1B-V2 is a tad cleaner sounding, though only slightly. There's no free lunch in audio, so the simpler signal path is audible. My LDR1B-V2 is now serving level matching duty of the bass amps to the mid/tweeter amps in my biamplified system. Speaking of which, having the variable input impedance capability (changeable on the fly from the listening position) on both Tortugas has proven to be invaluable in fine tuning the performance of the biamped system.
If you only need to input a single source, then the LDR1-V2 or the LDR1B-V2 will reward you with spectacular performance. By the way, using the optional battery power input takes any of the Tortugas to another level.