I usually try to recommend people that they always use c-s-v instead of setq. It's easier to explain and more consistent.
The fact that a lot of people use setq isn't really a great argument for using it in this case. The reason people use setq isn't because they want to, but because they don't understand how custom works. I see this as a great opportunity to make c-s-v more visible and teach people how to use it.
But setq doesn't have any concrete benefit other than familiarity to people who don't understand custom. I've spent more time than I wish on Freenode #emacs teaching people about custom. If c-s-v was used consistently that effort would be made a lot easier.
Regards,
Elias