I would definitely go for the wider tyre in this case. One reason is that the rims are steel and won't have a hook bead. This will restrict the maximum tyre pressure you can run. IIRC Schwalbe recommend that you lower the rated maximum pressure by ~15psi when running on non-hook bead rims.
cheers
ADVICE ON TANDEM TYRES PLEASE
Re: ADVICE ON TANDEM TYRES PLEASE
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~