As a rule of thumb, butter is used more in Northern Italian cooking. A good compromise, for health reasons, might be to use half olive oil and half butter. This way you also get the benefit of a relatively high burning point. Butter alone will easily reach the burning point, which is pesky.
For an optimal risotto, I would suggest butter only. This will improve your chances of getting the highly sought-after risotto all'onda, where the mound of risotto on the plate will slide when the plate is tilted.
I would not buy imported Italian butter,there is nothing special about it. Even when I was living in Italy, I actually looked for imported German butter; lacking that, I would try for the butter from the German-speaking region of Alto-Adige.
If you're unused to unsalted butter, give it a try for a few weeks. American-made Land o' Lakes is fine, as is the more expensive Danish Lurpak.
Whatever you do, avoid margarine and butter substitutes. Use less fat overall, but make it real.