It's a matter of personal preference of course. I like the Crane Suzu brass bells (they have copper and other flavors as well) and I mount them stem side. Sound nice, not too big and the striker lever can be rotated to any position so I can put it right where I want it. On a couple of my more modern bikes I use Spurycles on the handlebars.
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Pohl's law: Nothing is so good that somebody, somewhere, will not hate it.