Personally I'm more of a stereo in, stereo out kind of guy. The split obviously has to start somewhere in the chain, but with reverbs usually last in the chain that's not where I want it to happen.
Also a chain of pedals with mono in, stereo out, would make for some weird stereo connections.
Best would be stereo in, stereo out, but with the option of using one of the inputs as a mono and still getting stereo output.
Now that has been threadhijacked enough, doesn't the Belton brick have stereo provisions? I do seem to remember that not every pin is being used in a mono in, mono out setup.