The A B box will handle the effect sends, but you'll need a Y connector or something to handle the returns. The nice thing is that it (effectively) grounds the input of the unused circuit.
Alternatively, you could handle both inputs and outputs with a switch like this one:
This could be made into a stand-alone box, or built into a pedal with two circuits in it. As a stand-alone box, it will require six 1/4" jacks. The downside is that it won't ground the unused circuit input. That only matters on a few circuits, and if it's just for comparing pedals it should be fine. If it's used live, you should test the circuits for oscillation in bypass before you use it. (Just switch back and a few times while playing to make sure there's no unexpected noise .)