I personally use both, each for different purposes.

I snapshot my entire home directory every hour (using btrfs+snapper), but I exclude ~/.local/ from the snapshots. So I use ~/.local/bin/ for third-party binaries, since there's no reason to back those up; and ~/bin/ for scripts that I wrote myself, since I definitely want to back those up.

This is a pretty idiosyncratic use though, so I'd be surprised if many other people treated both directories this way.