I've used both. I used to have a William Evans double made in 1896 that was chambered in 450/400 3 1/4 inch Nitro Express. It was fun to carry and had a butt load of nostalgia on safari but my 375 H&H is a lot more accurate, better for longer shots and a lot easier to shoot a lot. The only source I had for factory shells was Kynoch and they sold them in 5 packs for $55 a pack. I got dies and handloaded them but I could load for my 375 a whole lot cheaper than I could load for the double.
In a fit of extreme idiocy I sold my double. Sure wish I still had it.
