Bottom, because it's been there a couple decades and although I've tried, I can't get used to it any place else.
There's a Linux distro (LXLE) that I won't use because it disables the "bottom" option for task bar location. It's one thing not to offer a choice, it's quite another to take away a choice that's normally there.
On the right of my left most screen in my 3 monitor setup. Puts it just to the left of my primary screen and makes it fairly easy to launch and switch apps without taking up primary screen space.