My feeling is that, while hi-vis is worthwhile, riding smart in traffic and keeping abreast of what everyone else is doing around you, is the best approach when riding in an urban area. Loud pipes do not save lives. All they do is irritate pedestrians and homeowners that you pass.
+1
I wear high vis riding gear these days. I figure it can't hurt, but I still ride assuming I'm completely invisible. I've never subscribed to the "loud pipes" theory. With all the sound deadening and thousand watt stereos in modern cars, all but the loudest pipes will be isolated, drown out, and just plain ignored. Hyper attentiveness to traffic patterns, doing your best to keep an escape route, and assuming that everyone is out to kill you is the best way to make sure they don't, IMO.
Pedestrians bring up another issue I've experienced now that I'm riding an EV. I've had a few now step right out in front of me and cause some pretty close calls. It's not so much an issue in parking lots or neighborhood roads as the bike makes just enough noise to get people's attention, but on a city street where the ambient noise drowns out the motor and belt whine, someone buried in their Facebook app has no way to know your'e there ('cause you know they're too busy to look).