Although broad generalizations about which volcanoes are especially hazardous can be hard to make. The style of eruption at Etna is much more mild compared to Vesuvius. In the past 79AD Vesuvius produced 10 cubic kilometers of ash and magma that killed many people. In contrast Etna produces more mildly effusive eruptions and is not as dangerous.

It's hard to say with volcanoes, because all it takes is a change in the composition of the magma feeding the volcano to cause a change in the volcano's behavior, and these can happen surprisingly quickly (for example, Krakatoa in Indonesia has always been an explosive volcano, but the unusually massive 1883 explosion may have been caused by a new magma mixing with an existing magma reservoir of different composition). Etna has had violently explosive eruptions - an eruption in 122 BCE seriously damaged a nearby town with ash-fall to the point where the Roman government exempted the town from taxes so that it could rebuild itself. As such it's difficult to say if Etna could have an explosive eruption as violent as the 79 CE Vesuvius eruption; Etna does not have the history of explosive eruptions that Vesuvius does, but all it takes is one freak event.

Vesuvius itself isn't consistent either: Vesuvius last erupted in 1944, but that was an aa-type eruption (pronounced "ah-ah", a Hawaiian word) that consisted of a 40+-meter wall of crumbling lava blocks, mostly solid but with a molten core, and moving at about 1-2 km per hour. This flow demolished villages as it buried them, but you notice from the slow speed that a human could easily escape it just by walking away, which is why, to my knowledge, this eruption caused no deaths.