Pula or Rovinj is the first planning question most people ask, and the answer is that they are different tools. Rovinj is the prettier town, smaller and more romantic, with a hill church and a harbour that belongs on a postcard. Pula is the bigger working city, cheaper, with the Arena, the museums and the beaches on the doorstep. You do not have to choose absolutely: with a car or the half-hour bus you can day-trip between them.
Price
Pula is cheaper across the board. A room in June runs roughly half the equivalent in Rovinj, and the restaurants follow the same gap. Rovinj charges for the looks, and most visitors decide it is worth a day even if they wince at the bill.
Getting around
Pula has the airport, the bus station, and city buses to the beaches. Rovinj has a bus station and a pretty old town you reach on foot, but no airport and no urban beach worth the name. If you are car-free, Pula is the easier base; if you drive, either works.
What to do
Pula has more to actually do: the Roman core, the Arena concerts, the museums, the diving, the day trips. Rovinj has the wandering, the dinner, and the boat to the islands. Couples and photographers lean Rovinj. Families and anyone on a budget lean Pula.
Our call
Base in Pula if it is your first Istria trip, you have a few days, or you want value. Base in Rovinj if it is a short, romantic break and you will happily pay for the setting. And if you cannot decide, base in Pula and take the Rovinj day trip: you get both, and the Pula travel guide frames the rest. For rooms, the where to stay in Pula guide sorts the areas.