If I select an object with a particular appearance, I can call Select > Same > Appearance command to select all object which have the exact same stack of the appearance attributes.

But if I have two objects with different appearances, and want to select all objects that have the same appearance as any of them (either of two!) — nothing is going to happen!

The command is active, but the selection stays the same... Not cool.

Sure, I can first find the first batch, lock or hide it, and then do the same for the second object, then unlock/unhide all to get a selection I need... but this requires nothing else locked or hidden :(