Multiple Trafo with single secondary vs Single Trafo with multiple secondaries

It is also more wasted heat in magnetisation current (iron + copper losses.)

One single transformer effectively shares its total VA capacity across all secondaries. You can draw far more than designed from from any combination, if teh remainder are under full capacity - that may be a 'plus' depending on use. In fact - big single transformers can withstand overload very, very much better , than a farm of little transformers each doing (sized-for) one-thing-only.
 
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