It’s really subjective, which one is better. Mostly just improves the flavor and the satisfaction of baking without yeasts. To adjust taste it’s a balance between time and temperature of proofing and quantities and qualities of the levain and dough.

To make the sourdough less sour/acidic you could try a fresher starter, using it as soon as it has fully risen and before it has developed the really tangy smell. Proofing the starter in the fridge may help make this time window easier, and proofing at cold temps should help make it less sour as well. Same with the dough, try shortening the proof time and/or proofing at a lower temperature.

You could also try doing a sourdough with a white bread flour to see if the spelt has a tangier flavor. Or you could try using a preferment with a poolish/biga to see how your wife likes that kind of flavor.