I've walked to the top of Vesuvius, and would love to follow that with Etna.
Whereas you can walk around the rim of the caldera of Vesuvius, they don't allow you near the top of Etna.
You go a long way up winding narrow road, passing remains of buildings half buried in black lava, till you reach a terminus where you get on a cable car that takes you part of the way up, then you transfrer to something like a small bus with caterpillar tracks.
After disembarking from that, we were escorted with a guide (sort of, it was a rather straggly group) a couple of hundred metres higher up the mountainside. We could only go as far as a chain barrier from which hung prominent yellow warning signs, and had to content ourselves with photographing the summit and smoke from there - not that we could see a great deal of it, because bad weather was closing in (it was the month of May).
It started to snow, and by the time we got back down to the Refugia, the volcano above us was covered white, while below us a big thunderstorm raged. In fact, we became trapped in the building by this storm, only venturing outside into the heavy rain some two hours later when the next bus arrived.
This was in 2001, before the last eruption which completely destroyed the Refugia and all that was associated with it.