We went to Herculaneum a few years ago. A very sobering experience to say the least.
I went to both. I liked Herculaneum more because there seemed to be a lot less tourists. I really got to take it all in.
Yep, I have visited a number of sites of pyroclastic flows. Fortunately long after they occurred. Recently, some lookie loos visited an active volcano in New Zealand during a cruise. A few of them actually survived. Spending your honeymoon in the burn ward is not a good way to go.