Peak season is a tax on popularity. Shoulder season is a refund.
Why it feels different
Restaurants have tables. Trails have sound. The light is often more interesting because the sky is doing something besides being perfectly blue.
You may need a sweater. You may get rained on. You will also get a place that still belongs to the people who live there.
How to pick
Look at school holidays and cruise calendars. Aim just outside them. Fly midweek. Stay in the second-best neighborhood.
The best trips are rarely the most convenient. They are the ones where the destination had room for you.