Spend more nights in Bologna or Verona?

That works
We did 3 in each ( no day trips)

But it depends on if you have day trips planned

Choices
From Bologna at least 1 day trip to a Ravenna
Another to Modena, Parma or Ferrara

From Verona to Vicenza or Lake Garda

Bologna is smashing in oh so many ways! The restaurants are unsurpassed, and I'm a vegetarian. Try their evocative and surprisingly vast Museo Archeologico. Having read every Italy guide book, including Rick Steves Italy, from cover to cover over the last three years, repeatedly, it is very clear that the way to enjoy CT and Vernazza is by staying the night but never the day. Confined minuscule spaces with hordes of tourists result only in all round asphyxiation. Other charming Ligurian coastal villages such as Camogli, Levanto and Santa Maria Ligure seem more than satisfactory.

Lucca is a complete hidden gem and warrants a minimum of 2 nights. Verona I try to avoid, as Rough Guide describes it as a "citadel of commercialism", RS comments that the Romeo and Juliet courtyard sight was invented in the 1970's, and all the rest of the sights are similar to what you can easily get in France.

It's interesting that at least Rick's 2018 guide says absolutely nothing about Bologna or, indeed, about the Emilia-Romagna region.

Yes. It is interesting, isn't it.

We recently spent 7 nights in Bologna (with day trips to Ravenna and Palma) and 3 nights in Verona (including one night at the opera). I think the 3 nights was just right - without any day trips.