You can put an Aprilia RS 250 two-stroke alongside a Ducati 916, an MV Agusta F4 and an Aprilia RSV4 and call them all Italian motorcycles. After that, the similarities get interesting. The RS 250 belongs to a very different period and engineering brief from the four-stroke superbikes. A Ducati Monster 900 adds another direction entirely: a naked road bike rather than a faired sport machine.
Ducati, Aprilia and MV Agusta show just how much variety can sit behind an Italian badge. There are V-twins and V4s, inline triples and inline-fours, with engines and chassis developed for very different jobs. An F3 RR and a Brutale 800 both use three-cylinder engines, for example, but the faired supersport and naked bike ask different things of their riders. The interesting comparison starts with the exact motorcycle, not the country written against the marque.
Italian marque heritage is not a guarantee about the factory that assembled a particular bike, the company's ownership at a given date or where every component was made. If you're narrowing down a model, start with its generation and intended road use; the marque story and the engine layout give you useful context without standing in for those details.