Regardless of what merge strategy you choose, install the MultiMerge gramplet … from the Isotammi addon collection.
If, for example, you find a dozen items citing the same page of a source, you would have to do 11 pairs of operations with the built-in merge. With MultiMerge in the Citations sidebar, you select all 12 and merge with a single operation.
The same when merging People or Events. I have not tested to see what happens with Event Roles during merges. We may have to ask @kku about whether differing Roles are preserved.